So I got the Panasonic PV-GS500, and I'm having the same problem. First of all, I use a Mac G4 Powerbook, and I wasn't able to download the software that came with the camera. Also, the Panasonic uses a USB out, not a firewire, which I think means I can't use iMovie! Anyway, regardless, the camera icon will never show up on the desktop when I plug it into the USB slot. I've tried various USB slots, etc, and various output settings on the camera like the playback, the PC Mode, etc, and no dice!
HELP!!!