ITunes not playing videos or movies

Question

iTunes isnt playing video's or movies, but is playing the music of them. I need help! I just purchased music video's and they are not playing, only the sound is.

Answer 1

This problem cropped up for me yesterday. I had just copied a new video to my iTunes library and was testing that it worked properly, but while the sound was playing, the screen was black.
Pausing/pressing the Play button resolves the issue, until I select a new video/movie to play, when I have to do it again.
I'm running MacOS X 10.6.6 and iTunes 10.1.1 (4). I tried reinstalling iTunes, with no luck. I also tried the old mainstay of replacing the Preferences file, but that also didn't help.
There is ONE new wrinkle to this situation. Yesterday, I had installed a new app named AirView to stream videos over AirPlay to my iPad. This works fine, but after this, the issue cropped up, suggesting an AirPlay issue.
I have two iMacs, so decided to try this situation on the Kitchen iMac and played a video on this other iMac just fine, video and sound. I then started up AirView on the iPad and initiated the video stream to the iPad from the Kitchen iMac. The movie played fine on the iPad. I quit AirView and went back to try the video on the Kitchen iMac, and yes, the video now failed to display until I reselected Computer from the AirPlay menu at the bottom of the screen, or used the pause/play solution, even though Computer was still selected as the default in the AirPlay menu. Doing this once seemed to be enough to resolve the issue for playing all videos on the Kitchen iMac, but not on the Office iMac.
The only other difference between iTunes on these two iMacs is that one (the Office iMac) is running its videos from a FireWire 800 attached 2TB hard drive, while the Kitchen iMac's contents are on the internal hard drive.
Deselecting the AirPlay option in Preferences/Devices to start videos correctly on the Office iMac is not a solution, since this iMac serves as our home server for our Apple TV.
Since I have a practical option, however, and since this issue doesn't affect playing videos remotely using AirPlay, this is now a buggy annoyance, but no longer a problem for me.