[Note: This post doesn't have any actual answers to your problem]
Not by my tower and camera to check right now, but do you [or anybody else] know if a camera will be shown in the system profile? I don't remember exactly, but I believe that it should.
My thinking is that if you can see the camera in the firewire bus section of your computer's system profile, you'll know that the computer is seeing the camera, and then you can begin trying to troubleshoot why FCP isn't seeing it.
If it's not showing up in the system profile [assuming that it would, normally] you could assume that the computer can't see it- in my experience this is usually a Firewire failure. Either the firewire port on the camera or computer has failed, or the actual FW cable. You can test any of those.
The only other advice I have is to reset the comp with the cam connected over firewire and turned on...
Good luck.