can't play .avi files in windows media player 11

I am able to watch an .avi file from my video camera once after that no more, It is not only me but my relitives are having the same issue, we are running XP, help we want to watch wedding videos, and show them to others.

I’ve never heard of such a problem before.
Can you feed the file into a diagnostic utility and report back what it says?
Instructions here http://www.moviecodec.com/topics/61931p1.html