iTunes video - plays audio, but no video? (Play fine in QuickTime.)

Hello.

Having an odd problem with the latest version of iTunes – when I attempt to play a video (purchased Apple content or my own home video), instead of displaying the video in iTunes, I get a black screen. The videos audio plays fine, all the video controls work, etc., I just get no picture. If I open the same file in QuickTime, the video plays just fine. Thought it might have something to do with AirPlay (having it set to remote speakers, which would be audio only), but this isn't the case. AirPlay is set to "Computer".

I've tried reinstalling iTunes, blowing out preferences, etc., but nothing works?

Any ideas?

Thanks,

Kristin.