| Is there a neat way to make this error go away?  In the instance I'm faced
| with, it only seems to happen when a keyboard is plugged in.  Is it time to
| find a new application for this fella?

On that machine I believe a level 15 interrupt is an async memory fault.
That is usually caused by parity or uncorrectable ECC errors from RAM,
although it could be caused by a bunch of other things, such as a flaky
cache, bad CPU, or even attempting to access a location that has no memory
or I/O device backing it.

First I'd recommend running the firmware's memory tests to see if they
show anything, which is doubtful since the memory tests usually aren't 
all that good.  Then try to get the AFAR and AFSR values for the faults,
either from the kernel or firmware, and see if there's a pattern.  Then
correlate the value of the AFAR with some piece of hardware and you'll
know what's borken.

Eduardo