diff --git a/apps/converter/api.py b/apps/converter/api.py
index 933962446d..395838ffba 100644
--- a/apps/converter/api.py
+++ b/apps/converter/api.py
@@ -26,10 +26,16 @@ QUALITY_HIGH = 'quality_high'
 QUALITY_SETTINGS = {QUALITY_DEFAULT:DEFAULT_OPTIONS, QUALITY_LOW:LOW_QUALITY_OPTIONS,
     QUALITY_HIGH:HIGH_QUALITY_OPTIONS}
 
+CONVERTER_ERROR_STRING_NO_DECODER = 'no decode delegate for this image format'
+
+
 class ConvertError(Exception):
-    def __init__(self, status, message):
-        self.status = status
-        self.message = message
+    pass
+
+
+class UnknownFormat(Exception):
+    pass
+
 
 def cleanup(filename):
     ''' tries to remove the given filename. Ignores non-existent files '''
@@ -38,17 +44,6 @@ def cleanup(filename):
     except OSError:
         pass
 
-def get_errors(error_string):
-    '''
-    returns all lines in the error_string that start with the string "error"
-
-    '''
-    lines = error_string.splitlines()
-    return lines[0]
-    #error_lines = (line for line in lines if line.find('error') >= 0)
-    #return '\n'.join(error_lines)
-
-
 #TODO: Timeout & kill child
 def execute_convert(input_filepath, output_filepath, quality=QUALITY_DEFAULT, arguments=None):
     command = []
@@ -58,10 +53,17 @@ def execute_convert(input_filepath, output_filepath, quality=QUALITY_DEFAULT, ar
     if arguments:
         command.extend(shlex.split(str(arguments)))
     command.append(output_filepath)
-    proc = subprocess.Popen(command, stderr=subprocess.PIPE)
-    return (proc.wait(), proc.stderr.read())
-
-
+    proc = subprocess.Popen(command, stderr=subprocess.PIPE, stdout=subprocess.PIPE)
+    return_code = proc.wait()
+    if return_code != 0:
+        #Got an error from convert program
+        error_line = proc.stderr.readline()
+        if CONVERTER_ERROR_STRING_NO_DECODER in error_line:
+            #Try to determine from error message which class of error is it
+            raise UnknownFormat
+        else:
+            raise ConvertError(error_line)
+        
 def execute_unpaper(input_filepath, output_filepath):
     command = []
     command.append(UNPAPER_PATH)
@@ -71,7 +73,6 @@ def execute_unpaper(input_filepath, output_filepath):
     proc = subprocess.Popen(command, stderr=subprocess.PIPE)
     return (proc.wait(), proc.stderr.read())
 
-
 def execute_unoconv(input_filepath, output_filepath, arguments=''):
     command = [UNOCONV_PATH]
     command.extend(['--stdout'])
@@ -82,7 +83,6 @@ def execute_unoconv(input_filepath, output_filepath, arguments=''):
         shutil.copyfileobj(proc.stdout, output)
     return (proc.wait(), proc.stderr.read())
 
-
 def execute_identify(input_filepath, arguments):
     command = []
     command.append(IDENTIFY_PATH)
@@ -92,14 +92,12 @@ def execute_identify(input_filepath, arguments):
     proc = subprocess.Popen(command, stderr=subprocess.PIPE, stdout=subprocess.PIPE)
     return (proc.wait(), proc.stderr.read(), proc.stdout.read())
 
-
 def cache_cleanup(input_filepath, size, page=0, format='jpg'):
     filepath = create_image_cache_filename(input_filepath, size, page, format)
     try:
         os.remove(filepath)
     except OSError:
         pass
-        
 
 def create_image_cache_filename(input_filepath, quality=QUALITY_DEFAULT, extra_options='', *args, **kwargs):
     if input_filepath:
@@ -125,7 +123,6 @@ def in_image_cache(input_filepath, size, page=0, format='jpg', quality=QUALITY_D
     else:
         return None
     
-    
 def convert(input_filepath, size, quality=QUALITY_DEFAULT, cache=True, page=0, format='jpg', extra_options='', mimetype=None, extension=None, cleanup_files=True):
     unoconv_output = None
     output_filepath = create_image_cache_filename(input_filepath, size=size, page=page, format=format, quality=quality, extra_options=extra_options)
@@ -142,36 +139,29 @@ def convert(input_filepath, size, quality=QUALITY_DEFAULT, cache=True, page=0, f
             cleanup(input_filepath)
             input_filepath = unoconv_output
     '''
-    #TODO: Check mimetype and use corresponding utility
     try:
         input_arg = '%s[%s]' % (input_filepath, page)
         extra_options += ' -resize %s' % size
-        status, error_string = execute_convert(input_filepath=input_arg, arguments=extra_options, output_filepath='%s:%s' % (format, output_filepath), quality=quality)
-        if status:
-            errors = get_errors(error_string)
-            raise ConvertError(status, errors)
+        execute_convert(input_filepath=input_arg, arguments=extra_options, output_filepath='%s:%s' % (format, output_filepath), quality=quality)
     finally:
         if cleanup_files:
             cleanup(input_filepath)
         if unoconv_output:
             cleanup(unoconv_output)
-        return output_filepath
-
+        
+    return output_filepath
 
 def get_page_count(input_filepath):
     try:
         status, error_string, output = execute_identify(input_filepath, '-format %n')
         if status:
-            errors = get_errors(error_string)
             return 1
-            #raise ConvertError(status, errors)
     finally:
         if output:
             return int(output)
         else:
             return 1
 
-#TODO: slugify OCR_OPTIONS and add to file name to cache
 def convert_document_for_ocr(document, page=0, format='tif'):
     #Extract document file
     input_filepath = document_save_to_temp_dir(document, document.uuid)
@@ -208,25 +198,13 @@ def convert_document_for_ocr(document, page=0, format='tif'):
     tranformation_string = ' '.join(transformation_list)
     try:
         #Apply default transformations
-        status, error_string = execute_convert(input_filepath=input_arg, quality=QUALITY_HIGH, arguments=tranformation_string, output_filepath=transformation_output_file)
-        if status:
-            errors = get_errors(error_string)
-            raise ConvertError(status, errors)
+        execute_convert(input_filepath=input_arg, quality=QUALITY_HIGH, arguments=tranformation_string, output_filepath=transformation_output_file)
         #Do OCR operations
-        status, error_string = execute_convert(input_filepath=transformation_output_file, arguments=OCR_OPTIONS, output_filepath=unpaper_input_file)
-        if status:
-            errors = get_errors(error_string)
-            raise ConvertError(status, errors)        
+        execute_convert(input_filepath=transformation_output_file, arguments=OCR_OPTIONS, output_filepath=unpaper_input_file)
         # Process by unpaper
         status, error_string = execute_unpaper(input_filepath=unpaper_input_file, output_filepath=unpaper_output_file)
-        if status:
-            errors = get_errors(error_string)
-            raise ConvertError(status, errors)        
         # Convert to tif
-        status, error_string = execute_convert(input_filepath=unpaper_output_file, output_filepath=convert_output_file)
-        if status:
-            errors = get_errors(error_string)
-            raise ConvertError(status, errors)
+        execute_convert(input_filepath=unpaper_output_file, output_filepath=convert_output_file)
     finally:
         cleanup(transformation_output_file)
         cleanup(unpaper_input_file)
diff --git a/apps/documents/views.py b/apps/documents/views.py
index 05b8699201..01d7ddb97f 100644
--- a/apps/documents/views.py
+++ b/apps/documents/views.py
@@ -16,7 +16,8 @@ from django.core.exceptions import ObjectDoesNotExist
 from django.core.files.uploadedfile import SimpleUploadedFile    
 
 from common.utils import pretty_size
-from converter.api import convert, in_image_cache, QUALITY_DEFAULT
+from converter.api import convert, in_image_cache, QUALITY_DEFAULT, \
+    ConvertError, UnknownFormat
 from converter import TRANFORMATION_CHOICES
 from filetransfers.api import serve_file
 from filesystem_serving.api import document_create_fs_links, document_delete_fs_links
@@ -509,6 +510,18 @@ def get_document_image(request, document_id, size=PREVIEW_SIZE, quality=QUALITY_
         filepath = document_save_to_temp_dir(document, filename=document.checksum)
         output_file = convert(filepath, size=size, format='jpg', quality=quality, extra_options=tranformation_string, page=page-1)
         return serve_file(request, File(file=open(output_file, 'r')), content_type='image/jpeg')
+    except ConvertError, e:
+        if request.user.is_staff or request.user.is_superuser:
+            messages.error(request, e)
+        if size == THUMBNAIL_SIZE:
+            return serve_file(request, File(file=open('%simages/picture_error.png' % settings.MEDIA_ROOT, 'r')))
+        else:
+            return serve_file(request, File(file=open('%simages/1297211435_error.png' % settings.MEDIA_ROOT, 'r')))
+    except UnknownFormat:
+        if size == THUMBNAIL_SIZE:
+            return serve_file(request, File(file=open('%simages/1299549572_unknown2.png' % settings.MEDIA_ROOT, 'r')))
+        else:
+            return serve_file(request, File(file=open('%simages/1299549805_unknown.png' % settings.MEDIA_ROOT, 'r')))
     except Exception, e:
         if request.user.is_staff or request.user.is_superuser:
             messages.error(request, e)
diff --git a/docs/CREDITS b/docs/CREDITS
index 7161417ef0..df0cded20d 100644
--- a/docs/CREDITS
+++ b/docs/CREDITS
@@ -108,3 +108,11 @@ PyMongo - is a Python distribution containing tools for working with
 GridFS - is a storage specification for large objects in MongoDB
     Copyright 10gen
     http://www.mongodb.org/display/DOCS/GridFS+Specification
+
+Image 1299549572_unknown2.png
+    Everaldo Coelho
+    http://www.everaldo.com/
+
+Image 1299549805_unknown.png
+    Oxygen Team
+    http://www.oxygen-icons.org/
diff --git a/docs/Changelog.txt b/docs/Changelog.txt
index f18cec4a91..86bc9f2109 100644
--- a/docs/Changelog.txt
+++ b/docs/Changelog.txt
@@ -1,3 +1,6 @@
+2011-Mar-07
+* Converter now differentiates between unknown file format and convert errors 
+
 2011-Mar-06
 * Fixed duplicated document search
 * Optimized document duplicate search
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