problem with ux400

[steven@linc.cis.upenn.edu]

We've been having a problem with our ux400.
Every so often, it pops into the cold load stream with the following error:

--> Error in the dispatcher, using the cold load stream <--

Trap: The second argument to the %32-BIT-DIFFERENCE instruction, #<DTP-PACKED-I
NSTRUCTION- 77 37777777777>, was not a fixnum

PROCESS::UDPATE-PROCESS-METERS
   Arg 0 (PROCESS::PROC): #<PROCESS::SIMPLE-PROCESS Main X Blinkers UNAGI:0.0 0
(Genera on GLENSIDE) (0 500000) 1055205>
   Arg 1 (TIME): -2046770035
s-A, <Resume>: Supply replacement argument
s-B:           Return a value from the %32-BIT-DIFFERENCE instruction
s-C:           Retry the %32-BIT-DIFFERENCE instruction
s-D, <Abort>:  Restart process Main X Blinkers UNAGI:0.0 0 (Genera on GLENSIDE)


It happens for different processes (e.g. Ethernet, Main X Screen) as well.
Glenside is the name of our UX-400 board- it is embedded in Unagi, a 
Sun 4/280.  We're running genera 8.0.
We don't have the source for this function.
Any ideas?

Steve.
Linc Lab, University of Pennsylvania.