Scott,
Is this an XP or Vista machine?
Have you tried deleting the Red .ini file. It is located in the C:/Windows folder and should be BorisRed4.3.ini.
Trash that and see if it performs any better.
Also you noticed this only after reverting back to 7.1.6 QuickTime?
What version of QuickTime were you running before and if you go back to it does it work?
-Matt