Problems with media player playing WMVs

Windows media player 11 (11.0.6000.6344 latest available version) running on 32 bit Vista.
WMV files were playing just fine two days ago. Now I get error code C00D11D2 which is a general all purpose something’s gone wrong kind of error.
I haven’t had much help from microsoft’s windows media help pages. Lots of people asking the same or similar questions with some stock answers but nothing that illuminates what is going on with my machine.

Error message reports that media player cannot find the file, does not have access to it or proxy settings are not correct. Other comments on the message board are to install codecs or to stop trying to cheat copyrights. WMV codecs are supposed to be installed with mplayer. The files are of my own creation and played just fine two days ago. So I can’t see that any of the solutions offered are applicable in my case.

I would like a simple solution without having to uninstall and reinstall media player if that is possible.
Help much appreciated.

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