i have seen this error on machines that have one of those installed:
http://www.free-codecs.com/download/Cod ... l_In_1.htm
they hook into the system and divert the calls to render the tumbnails, and other grafic content.
http://www.softpedia.com/get/Multimedia ... Pack.shtml
there are many of them.
especialy the ffmpeg component is very buggy