for about 2 weeks i have been using a usb cf reader.  up until today, it
would attach at boot time, and it would attach as a usb 1.0 device.  i
did not have support for usb 2.0 (ehci) built into my kernel.

this morning i plugged in a usb midi interface while ripping a track
from a CD, and my computer locked up solid, wouldn't even respond to a
ping.  i power cycled and resumed using my computer, it seemed fine from
there.

this evening, i noticed that the usb cf reader was no longer
present.  i PUP'd it (phyiscally unplugged and plugged), and now it
showed up again, attached as a usb 1.0 device.

so i tried rebooting, and it still did not show up.  i tried the GENERIC
kernel, and it still did not show up.  I tried other usb ports, and it
still did not show up.  I tried enabling various kernel debugging
options related to usb and scsi, and it still did not reveal anything.

searching through gnats revealed kern/25683, which looked similar.
i tried physically powering off the machine, still no dice.

i enabled support for usb2 in my kernel, and saw this:
uhub3: device problem, disabling port 5

when i PUP'd the device, it attached as a usb 2.0 device.

i reboot, disable usb 2.0 in the bios, and now the device attaches at
boot again, as a usb 1.0 device, as i was accustomed to seeing.

i cannot say why the device wouldn't attach at boot with usb 2.0
enabled, and why it stopped working today after 2 weeks of use, and no
known change to the hardware or software configuration.