This is a little weird, and could be sheer coincidence, but I have two devices
that inexplicably depower sometimes while being used on a NetBSD box; both
devices used to work just fine.  By possible coincidence, both are
keyboard-like devices.  One is a USB keypad, the other is a PS/2 adapter.
In both cases, the device will run fine for a while, and then, a while later,
it'll suddenly be dead.  Unplugging it, and plugging it back in, fixes it.

This may or may not be related to my ongoing problems with 7-port hubs and
multi-function devices being utterly random and useless.  *sigh*.

-s