I didn't want to have to go down this way at first but...
If what you see shouldn't be happening, and it doesn't happen on another machine running the same software, then it's time to trash the preference files. If that fails, then a reinstall is in order. But an uninstall should happen first with this software: http://www.digitalrebellion.com/fcsremover/
FWIW, at the school I teach at, we erase and reinstall a clean OS and apps on 50 Machines every semester. We have stability that way. There are 450 students sharing these stations. We don't see problems much. Long ago I started doing a clean install on my own machines about every year. World of difference when you do this.
If the machine you're running is busy, and over a year old, and you've never done this, it's likely a thing that will improve the whole experience there. It can be argued too that if the machine is dedicated, you should run the version of OS with the version of FCP that it was written for. Lion is as far as you go I'd think. Apple blessed FCP 7 and Lion, but hasn't Moutain Lion as far as I know. Either way, if you do this, clone the drive first, or buy a new drive and put it in etc... keeping the startup disk you have now. I just rebuild myself. backup docs, downloads, mail etc, and then copy them back... works fine.I don't run FCP 7 on Mountain Lion though. Lion's OK I think. I run FCP 7 and X. I've a dedicated startup disk for FCP X however.
Actually, Snow Leopard actually was really great with FCP 7.03. All of the third party stuff worked great. AJA, Blackmagic and Matrox, as well as the the plugin world's goodies.
Jerry