Could be a lot of issues.Could be your computer isn't powerful enough to power the program and Aero. Could be your video driver is out of date. Could be that you're using the 64-bit version of Windows 7. Could be your antivirus, especially if you're using McAfee or Norton. Could be any of a number of other issues.
But I certainly recommend shutting down Aero and the sidebar, not matter how powerful your program is, if you're trying to edit video. They just drain power.
You should check you have the most recent graphics driver from the manufacturers web site. You do need the latest version of Apple QuickTime (7.6.9 at time of writing). I have W7-64 bit, use Aero, and I have qttask disabled - these do not cause me any problems with PRE.
Insanity is hereditary, you get it from your children
Thank you Steve, I've shut down Aero anyway and have restored PRE functionality. But is qttask a necessary component of PRE? The reason I suspected qttask.exe was that Win 7 put up an error msg suggesting that there was an incompatibility issue between qttask and the windows color profile and that it would be altered whilst qttask was being used.Thanks again and to Neale, John M