It is odd Wolfgang, WMP can play the file and WLMM cannot.
It took me a while to find this, not sure it applies or will help. On the MS board
, there's mention of a Fixit as well as an opensource codec checker.
I've found that for the most part codecs are system wide, except where an app such as VLC maintains it's own set.
I also found references to turning off transcoding and or specific codecs. Again, I'm not sure if that applies or will help.