its funny. i bought an iomega fw400 external the other day (its one of those with like 8 ports on it designed to attach to a mac mini).
it met most of my specs, (couldnt say what chipset it used) so i bought it as it was all that local dealer had that even came close. so i brought it home, formatted it mac extended but i was surprised by the fact that it consistently dropped frames and froze on capture.
just as a test, i moved the whole of the project files (capture scratch, source files etc...) to the drive and its been working like a champ ever since - go figure ?