I had the same problem. Though it seemed to affect all QT files that were local including Sorenson MOV files and all of my MP4s. Thouigh not stuff online.
😕
Ultimately I beleive the solution was to upgrade the drivers for my video card, although at around the same time I removed Quicktime and reinstalled it from the standalone installer.
So, I'd suggest: Remove QT7.1.3, Upgrade your video driver to the latest available, reinstall QT 7.1.3.
Here's the URL my QT installer was from:
http://appldnld.apple.com.edgesuite....com/mcgonagail/us/win/QuickTimeInstaller.exe
B