iTunes after 10.8.3 combo update doesn't play video, only audio with a black screen

My iTunes has been randomly playing really old QuickTime files as I've had iTunes start in 32 bit mode. That worked for a while, but like I said, it has stopped working and iTunes is back to not playing older QT movie files. Fine.

Now, however, iTunes didn't play a PROTECTED file that I purchased from the iTunes store. I made sure my computer was authorized to play the file, the store said my computer was already authorized. iTunes plays the AUDIO of the selected video, but only shows a black window where the video should be playing. It did this for several videos. I was confused.

I restarted my computer and now iTunes is playing the file as it should. It is not however playing my MPG QuickTime movie files that it has played for years.

What is going on with the software? I've followed the threads telling me to remove Perian, remove, Filp4Mac, restart, run in 32-bit mode, etc and nothing is now working when those solutions worked just last week.

Any input about what I should try next would be greatly appreciated. Thanks!

Chad