My preferred way to clear the prefs is to quit PPro, rename the "Profile-<username>" folder under Documents/Adobe/Premiere Pro/8.0, then launch PPro. When it can't find the old prefs, it will write new ones. If that does not resolve the problem, then you can delete the new Profile folder and revert the old one to it's original name, so nothing lost.
But first, I'd try Abhishek's recommendation. I defer to him when it comes to troubleshooting such issues. BTW, I'm nearly certain he meant "safe" mode.
