MovieMaker 2.1 not working after upgrading to Media Player 10

MovieMaker 2.1 was working fine 6 weeks ago.
A month ago I downloaded Media Player 10 (for XP SP-2). Today I was unable
to input data from my digital camcorder into a working *.WMV file. I got a
'Unknown Error' message each time. I could import to an *.AVI file. After
editing a movie from video imported previously (*.WMV file) I discovered I
couldn't output the finished movie in any format - "... Movie Maker cannot
save the movie to the specified location. ..."
I assume this due to changes in the codec. Has anybody found a work around
for this?
--
Kim