Windows Media Player encountered an unknown error.

When I try to view a mpg, wmf, avi, etc. movie, I usually
receive the error message "Windows Media Player
encountered an unknown error." about 70% to 90% of the
way through. Also, occassionally when I view a mpg, wmf,
avi, etc., the time/length of the show is incorrectly
reported as a much lower figure that it really is.

I am using Windows XP Home and the most current Windows
Media Player, with all updates.

FWIW, I can use Real One Media Player without any such
problems.

How can I correct the Windows Media Player problem?

Thanks,
Ron