Help! Does anyone know why we crash? (4.2bsd)

[matt at oddjob.UChicago.UUCP]

Lately the system keeps crashing after several days of uptime.  The console
messages are always like this:

uba0: too many zero vectors
uba0: reset dz0 dz1 dz2 uda0 ec0
uba0: uba error sr=1<UBSSYNTO> fmer=0 fubar=0
uba0: uba error sr=10<IVMR> fmer=40 fubar=772150
uba0: uba error sr=1<UBSSYNTO> fmer=0 fubar=0
	... ( 7 more repetitions of that line, and then ) ...
ERROR LIMIT uba0: reset dz0 dz1 dz2 uda0

and it crashes.  Our load average is usually high ( 7.00 to 25.00 or so ).
We have one UBA, which holds 3 dz11's, a 3COM ethernet board, an RX211
floppy disk controller (seldom used), and a UDA50 with 2 RA81's

Is this a known bug?  We don't get a core dump, so I don't know where to
begin looking.  Oh yeah, it's a 780.
___________________________________________________________
Matt		University	ARPA: crawford at anl-mcs.arpa
Crawford	of Chicago	UUCP: ihnp4!oddjob!matt