I have now had the same problem two times with I Movie and or my camcorders. A few years ago I bought a mini DV tape based camera (panasonic) and it worked well for a year or so. Then, poof, the camera would not show up in I Movie no matter what I did, reboots, new firewire, on and off, etc...nothing. So, buy a new camera, a Canon 930, Mini DV tape - worked great for a year and a half. Same story. Poof..... The firewire is good, I tested yet another camera (borrowed from a neighbor this time), which connects to I movie without issues.

Any clues??