re-posting for data loss from server crash.
Do you have a restore point from before this problem started you could go back to? System Restore
If you installed any codecs you could try uninstalling those to make sure they are not the cause of the problem.
You could run a System File Check to make sure there are no issues. SFC /SCANNOW Command - System File Checker
You could also try turning off WMC, rebooting, and turning back on WMC to see if this will reset something to fix this.
If you do this I expect you will lose all your current configuration settings, customizations, etc.
Re doing those changes may be a bit of work for you...
hope this helps