My problem is similar. I can play music, but I cannot play any movie or video (including SD). Whatever point I start the movie at I can see a frozen image and I get about 5 seconds of audio, then the audio stops and the movie never advances (neither does the time-counter).
Here are my system specs (all of which meet or exceed Apple's requirements):
OS: Windows7 64-bit
Processor: 3.30 GHz AMD FX-8300
RAM: 32 GB (16 GB usable) DDR3 15600MHz
iTunes version: 10.7.0.21
Video: AMD Radeon R9 270 (verified with manufacturer - supports HDCP)
Display: Samsung SyncMaster 2333HD (verified with manufacturer - supports HDCP)
Resolution & connection: 1920x1080, HDMI
I've reviewed and checked all system requirements - all are met.
I've reviewed and verified all requirements listed in ts1718 (Troubleshooting iTunes for Windows Vista or Windows7 & video playback performance issues).
I tried jamesfromcommack's idea as well as all the recommendations listed in all the associated posts and articles I could find, none of them have resolved my issue. I know what the requirements are, and I meet or exceed them all. Can you or anyone provide any other assistance?
Thanks (in hope)