Quit, delete the preferences folder, and then restart.
The preferences folder is here: <drive>\Users\<username>\AppData\Roaming\Adobe\Adobe Premiere Pro\
Also, be sure to run as administrator. You can right-click the Adobe Premiere Pro program icon and choose to run the program as administrator in Windows 7.
You should also check out these troubleshooting tips for QuickTime issues:
That was written for After Effects, but the same things apply to Premiere Pro.
Thank you for the suggestions Todd. So far so good with trying the first one only. I need a few more hours of work before I know if it worked. I'll post results then.
I've worked for about 8 hours without a crash so that suggestion seems to have done it for me. I can close and reboot with no problem and it never crashes now. Thanks! I have CS3 installed also and I deleted that folder from both versions. My guess is that running the trail version of CS5.5 without uninstalling CS3 is a problem. At least delete that file. I still haven't uninstalled CS3 but I'm sure I'm never going back and should nuke it.
A few minutes after writing this the problem returned and I had to reboot the computer for PP to work.