[LAD] snd-usb-audio dying on jackd xruns

So I start jackd and it runs fine for a while. Then ALSA crashes and triggers an xrun. Jackd continues to do its merry thing - minus the part about spitting info out to my soundcard... I've tried multiple usb intefaces. All work fine with other computers. I've tried multiple version of Ubuntu with various versions of ALSA. Only this machine is affected. I have 3 other machines that run these interfaces just fine... So it seems to be a hardware compatibility issue not a software glitch in one version. I've tried many boot flags but to no avail. Am at a loss on how to troubleshoot. The machine is M4N75TD motherboard with a Phenom II 1055T and the latest bios flash. ...Rods ;-)