Capture One Pro 5.0.1

Hi, I was working in a session in the morning. I exported several files made corrections to some with no problem. Then I opened several other sessions through the open session dialog box and worked on those files. I went back to my other session I worked on in the morning and the program crashes before it can switch? I'm running version C1 Pro 5.0.1 on a macbook pro with Snow Leopard 10.6.2 Is there some other pref file I can purge to fix this. Like I said it worked fine in the morning but I can't open the session in the afternoon. I have not had any crashes or other problems it just happened all on it's own.

Thanks

John