I had the same problem earler today
the problem came about after installing a
'Fraunhofer IIS MPEG Layer-3 Codec'
(must have been clashing with a previous version)
i solved the problem buy uninstalling any codec appliance id installed such as real altenative quick time alternative, divx, xvid, ac3, ogg, etc
i also searched the registry using the term Fraunhofer to remove all refrences to the offending codec.
The Fraunhofer codec did not have an uninstall function available.
PLEASE REMEMBER TO EXPORT YOUR REGISTRY 1ST IF YOU USE THIS METHOD.
Then installing the latest k-lite full codec pack. using the setting 'lots of things' when installing. now all is good
get the klite codec pack here
http://www.afterdawn.com/software/video_software/codecs_and_filters/k-lite_codec_pack_full.cfm