Windows Movie Maker and m2v files

For the past year or longer, I have used Windows Movie Maker to edit video m2v files. WMM would never recognize the m2v extension. But if I renamed it to an "mpg" extension, WMM would load the file with no problem and I could proceed with my editing. But now I'm having a problem...

Due to unrelated problems with my PC, I had to reload the OS. After the restore, my system is running much smoother. Except that now WMM won't recognize the same m2v (renamed to mpg) files. It gives me this error:

Filename.mpg could not be imported. An interface has too many methods to fire events from

What does this mean? And what do I need to do to get WMM to recognize these files again so that I can continue my video editing like before?

Thank you very much.

Sincerely,

Jordan