How do I check my codecs are working?

I bought the MPG2 and VC1 codecs but I have no way of knowing if they are working as the command vcgencmd codec_enabled MPG2 or WVC1 gives the error:

 

VCHI initialization failed

 

How can i test if my codecs are installed and working properly?  Or is this error suggesting something worse is wrong?

 

Thanks

sorry - looks like same issue as this:

http://forums.plexapp.com/index.php/topic/66619-issues-with-codecs/