Firewire Audio + OS X 10.6.8 = Recording Glitches?

I'm getting constant glitches when recording audio under 10.6.8. Happens no matter what audio recording program I use. I'm having the glitches on two different Macs, both with 10.6.8, and two different soundcards (Ecler Evo 5 and Edirol FA-101). I'm having them whether I go in digitally or analog, though the glitches sound different, and I'm having them recording in traktor, Audio Hijack, and SoundStudio. I don't hear the glitches when I'm playing but they're there when I play back the recording. Results are uniformly unlistenable.

Is anyone else finding Firewire Audio actually working in this configuration? What about USB? I didn't have these problems when I used the Audio 8 a lot but I think that was in previous systems. Help!