hardware problems?

[Marrq]

Hiyas,
	I think that I have a hardware problem, but have no clue as to how
to possibly track it down.  I have a 3c900 revB ethernet card, and this is
causing my machine (dual PII 266mhz, 64M, Super Micro P6DLE motherboard) 
to opps like crazy.  I have the oppses and the output after running it
thru ksymopps at http://ack.caltech.edu/~marrrq/opps/ .  The output from
vortex-diag is at http://ack.caltech.edu/~marrrq/opps/vor/ .  The oppses
seem to be in fairly different places to me.  I suspect the motherboard
(this is the third one I got (the other two were beyond dead on
delivery)), however I would like to know the best route to track this
down.  Note, that the ethernet card works perfectly in my pentium system
(generic system bought from gateway in late 1995), and if I move the
kernel the pentium was running (no modules capability) to the PII system,
it will opps.  My typical test case which I use to get my machine to opps
is to have to processes, one ncftp putting a copy of /proc/kcore to my
pentium (on the same hub), one getting a copy of kcore.  The opps will
occur with only one process transfering, however having multiple processes
running triggers it quicker (usually before both have moved 5Mb). 
Question, if everything was working correctly should I have busmastering
disabled or enabled in the bios?  I've tried it in both configurations and
get the oppses either ways.  I am sending this to this list because the
card triggers it, and you might be familiar with the code areas.  If I
should send this to someone else/some other list, please let me know.  It
should be noted that my system is rock solid if I don't use the 3com card
and instead use a generic ISA NE2000 card (however not using the 3com card
isn't an option (well, it is, but the point being that I want to get
working hardware, rather than buying something new, and finding out that
it is the motherboard that's bad, and having passed warranty deadlines)). 
If more info is needed, please ask.  Many thanks in advance... 

	-marrq