[LAU] usb soundcard: xruns and latency even with -rt kernel

I'm using an M-Audio Transit usb soundcard with the kernel 2.6.22-rt,
as packaged by ubuntu. I'm running jack right now with -p 3 -n 512,
and I still get xruns, typically of values less than .03ms, every few
minutes. Increasing the jack latency reduces the rate of xruns, but I
can't eliminate them without using settings large enough to cause
noticeable delay. I've raised the priority of the IRQ-16 process (the
one controlling the usb bus with the sound card); I also tried to use
setpci to tweak pci latencies, but for some reason the settings
wouldn't apply (when I read the values back, they haven't changed).

I've posted the results of rt-setup-report.sh (plus lsusb) at
http://artdent.homelinux.net/~jacob/rt-setup-report . Is there
anything else I can try?

Thanks,

-- 
Jacob Lee
artdent@email-addr-hidden
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