When I did ctrl-alt-F1 to switch to a virtual console, I was looking at the following line being repeated 10 times per second, unstoppable:

ALSA /build/buildd/linux-ubuntu-modules-2.6.24-2.6.24/debian/build/build-rt/sound/alsa-driver/usb/usbmidi.c:193: urb status -32

(i "dmesg" in the terminal to take the time to copy the message)

Any ideas what this is all about? I've never seen this again.