So I recently decided to install the trial of Premiere Pro CS5, in order to try it out before buying it. I worked with it all day the first day I installed it, and it worked wonderfully. The moment the clock hit midnight, however, and my first day of using it was up, it started acting up! Everything still worked fine, but ever since then, any time I've tried exporting the short (3:20) movie project I'm making, it freezes.
Reguardless of the time it says I have left till it's done creating the file, it freezes consistently at 79% saved. An error message pops up saying (don't remember exactly) that it's like a 758 error and premiere couldn't finish the project and needs to close... Once I hit the only option, "okay," premiere closes and I have an unsuccessfully saved .avi file on my desktop... Which obviously doesn't open.
It's always good to include some basics on what kind of system you're using when posting as the system (Mac or PC) specs are greatly influencing the overall experience.
That being said, it sounds like you just need to trash your preferences.
You could also try clearing your media cache (which is in Premiere Pro's preferences panel)
I hope this helps.