A bump to this old thread to share my story.
Had a mk I since they came out, always been solid. Just got a new iMac, bought a La Cie Firewire 400 to 800 to do a migration of stuff from my old plastic MacBook, all went fine, Then I connected the Ultalite and after a few minutes got the same as the OP. This happened a couple of times over the next few days. The rest of the time, the UL worked fine but maybe once every few hours audio would cut out for a second before returning.
So I got a different cable, a Moshi connector, which I connected to my original MOTU 400-400 cable. It's been a week now and everything is back to normal. So in my case (fingers crossed) the problem doesn't seem to be the UL but rather the faulty La Cie cable which doesn't seem to do buss power well, at least on my system.