Vista - Intermittent "necessary files not installed or are corrupt" error when trying to play .dvr-ms files in VMC

I get this error occasionally when trying to play recorded TV files (dvr-ms)
in VMC, and the suggested restarting/rebooting doesn't help. My only
recourse is to restore a disc image made when things were working correctly.

I mainly use TheaterTek or ZoomPlayer for multimedia files and sometimes
need to use GraphEdit to analyze/create playback graphs. Is it possible that
this experimentation with filters/renderers, etc. (which sometimes causes
GraphEdit to crash) corrupts the default graph that Vista uses? Is there any
way to troubleshoot this? VMC error messages are so vague, it's hard to tell
exactly what is going on (Event Viewer, as far as I can tell, isn't much
help either).