booting with usb keyboard hangs system

[Matthew Dillon]

    Also try the emergency interrupt polling code.  If the usb keyboard
    works with the emergency poller but doesn't work otherwise then we
    will know that it is an interrupt related issue.  If that turns out
    to be the only solution then you would also probably have to increase
    the polling frequency from 10 to 100 (it is 10 by default because we
    want people to notice that interrupts are broken instead of just always
    relying on the emergency interrupt polling thread).

    In /boot/loaderconf:

    kern.emergency_intr_enable=1
    #kern.emergency_intr_freq=10

						-Matt