Don't know if you have solved this yet, but I had the exact same problem with
the ed driver using a Micron P90 with an SMC Ultra board.  The solution was to
move the RAM address from CC000 to either D8000 or DC000.  Either worked fine
for me.  You'll have to rebuild a kernel to change it.  I never did find out
what was conflicting with it ( I have a BusLogic SCSI board with ROM set to
C8000, but moving it to D8000 still gave the same problems, and all of the
memory caching/shadowing is turned off.  The really weird thing is that I was
able to use the board set to 10/300/CC000 with the install floppies to FTP
down all the gzip'd install files ( bin10.* etc10.* ... ), but when I rebooted
with everything installed, it started giving me the NIC memory corrupt
errors. )  Regardless, switching to a different RAM address worked for me.

Hope this helps,

--Brian