[Sunhelp] Ethernet puzzle

[Gary Gendel x3145]

I recently upgraded my 10base-T hub to a 10/100 base-T unmanaged switch 
(D-Link DPS8+8).  I just had an anomally that puzzles me....

I shut off an Ultra-10 dataless client unless needed.  The unit has the 
inexpensive Sun supplied ethernet board.  Last night when I turned on the 
machine, I got a message about the network not being connected, Cable problem? 
 Anyway, rebooting or power cycling the machine didn't help, changing ethernet 
cables had no effect, and power cycling the switch didn't help either.  I 
finally got it working by plugging the Sun into the old 10base-T hub.  Once 
the ethernet line was up, I unplugged it from the hub and into the switch and, 
voila!, 100base-T was up and running.  Power cycling the Ultra afterwards 
didn't cause the problem to re-appear.

I don't know whether this is an anomally or something that will happen again  
Does anyone have an idea of what happened?  If it happens again, what should I 
do to isolate the problem?  I suspect the switch, but then again it was 
plugging the Ultra's cable into a 10base-T hub that seemed to cure the problem.

Thanks.
Gary