maybe it's your capture cam. I used to play around with those small Panasonic cams and how frequently they would get recognized, once plugged in, by my personal, work, or friends' computers was super inconsistent. actually I could never get them to work with Firewire ever - only USB ever worked (only on certain PCs - never Mac - and whenever it felt like), but somehow I could still capture the footage without any quality loss that way. not the recommended method though.
also you couldn't even just play tapes of VX footage on most of them, although I suspect that might have had to do with some kind of PAL / NTSC incompatibility when the capture cam is of a different origin than the original cam (but please don't take my word for that, I'm no technician)