applied fix as mentioned in http://ar-code.lighthouseapp.com/projects/35/tickets/16-imagescience-gif-thumbnail-references-incorrect

lib/technoweenie/attachment_fu.rb

@@ -235,7 +235,7 @@ module Technoweenie # :nodoc:
           ext = s; ''
         end
         # ImageScience doesn't create gif thumbnails, only pngs
-        ext.sub!(/gif$/, 'png') if attachment_options[:processor] == "ImageScienceProcessor"
+        ext.sub!(/gif$/, 'png') if attachment_options[:processor] == "ImageScience"
         "#{basename}_#{thumbnail}#{ext}"
       end