Why can't i watch .avi files on windows media player?

I have an ortment of video clips that I just transferred to my new comp. I downloaded a codec package that included the ones i used before (DiVx and FFD show) but for some reason, my .avi videos don't play on WMP, instead they're kind of frozen in this frame-by-frame mode where nothing moves but if i drag the seek on along the images flash up at the right times, and there's no sound. the .wmv clips work perfectly fine. I've also tried and sucessfully watched these .avi clips on windows movie maker. is this because movie maker is filtering something windows player isn't? HELP! oh and these .avi files were translated from .flv files, so is that why i'm having problems? my old windows player was windows media player 10, this one is 11.