Check that you have the very latest video driver from the mfgr's. Web site, as that has caused similar for many.
Thank you for all your help Mr. Hunt. This is the EXACT problem I'm having: http://forums.adobe.com/message/2270418#2270418 . My computer says my driver is Up to date, and I tried un-clicking "enable gpu playback". With no luck. What do you think?
Make sure you have the very latest version of QuickTime (v7.6.6 at time of writing) installed.
Insanity is hereditary, you get it from your children
Fixed! It was just a Windows Update that hadn't been updated yet. Works like a dream now. Thanks you guys!
People are always skeptical when we suggest Windows, Quicktime and video driver updates -- but they do fix about 90% of the problems!
Glad you're up and running, Craig!