Yes I have trashed my preferences.
Yes I have repaired permissions.
The problem is not a result of conflicting serials on the same network.

I was working in FCP with iTunes open when both started to act a little wonky. Hanging and glitching a little. I saved my work, closed all the programs, and restarted. After restarting, I click the FCP icon, it bounces once, and then nothing.

Here is what the console says:
7/12/10 9:34:50 PM com.apple.launchd.peruser.501[118] ([0x0-0x2c02c].com.apple.FinalCutPro[365]) posix_spawn("/Applications/Final Cut Pro.app/Contents/MacOS/Final Cut Pro", ...): Permission denied
7/12/10 9:34:50 PM com.apple.launchd.peruser.501[118] ([0x0-0x2c02c].com.apple.FinalCutPro[365]) Exited with exit code: 1

I deleted the preferences manually, before downloading and using FCS Maintenance Pack to clear caches and preferences again.

I've restarted multiple times.

OS X: 10.6.4
FCP 6 (not sure the exact version because I can't open it to check but it should be fully up to date)

I welcome any ideas and help. The only thing I haven't done yet is reinstall.

EDIT: in the console dialogue, where it says "permission denied" used to say "Folder or Directory does not exist". It changed to permission denied after I put a folder in. I then attempted to repair permissions again to the same results.