Hang during USB device probes on CURRENT

I have a Dell Dimension 8250 with typical hardware (RAMBUS option). With 
recent CURRENT, it seems that whenever a USB device is probed, FreeBSD 
will just hang.  It will not respond to a three-finger salute, it will 
not respond to the ATX power switch and it will only respond to a hard 
boot via the power switch.

I am not all to familiar with debugging the kernel, although what I was 
able to read in the FreeBSD documentation only applied to kernel panics 
and not out-right freezes?  Is there a procedure I can follow to aid 
with finding the cause of this?

Thanks in advance,

Tom Veldhouse