Windows Movie Maker sound out of sync

Hi!

Sometimes when I try to edit a show that I captured on the TV card, the
sound gets out of sync. When I play the show on the Media Center, the sound
is just fine, and the sound in later parts will sometimes be fine, but after
cutting out the commercials, the sound will get ahead on the video on some
parts, until the place where the commercial is cut and then it gets back into
sync. The previews don't show it doing this.