FATAL: Parity error on add-on card. What does it mean ? (ISC 2.2)

[Steintor Bjarnason]

My computer (Tandon 386/33, 8MB memory, Adaptec 1542 scsi controller) has
been crashing a lot lately with the error message :
  FATAL: Parity error on an add-on card.
  PANIC: Parity error address unknown.

Also when I have used shutdown to stop ISC then it has crashed with a :
   PANIC: Kernel mode trap.  Type 0x0000000E

My add-on cards are:
  Racal Interlan NI6510 Ethernet card, INT=12, I/O=360-36F, DMA=3
  Datatalker PC/XL 3270 card, INT=5, I/O=2A0-2AF, Shared Ram=D8000-DBFFF
  Netcom II, RB14 X.25 card, INT=15, Shared Ram=D00000-D80000
  Adaptec 1542 SCSI controller, INT=11, I/O=330-333, BIOS=C8000-CC000
  Paralell/Serial card with LPT1,COM1 and COM2. (INT=7,3,4, 
                                                 I/O=378-37F,3F8-3FF,2F8-2FF)
Computer:
  Tandon 386/33mhz with 8MB memory running Interactive Unix v2.2.0
  660 MB Storage Dimension SCSI disk.

Strangly enough, this setup worked perfectly for about 10 months but my 
computer started to crash about 1/2 month ago.  I have tried to replace the
X.25 card and also removed the 3270 card but it still crashes.

Is this a problem with my add-on cards or a problem with the main memory ?
If the main memory is faulty, then shouldn't I get a "Parity error at ..." or
a "Parity error unknown." ?
  
Is it possible that my Ethernet card or the Paralell/Serial card is giving
me problems ?  These cards don't contain any memory.

Please e-mail if you have any suggestions. 
  Steintor
  
-- 
Steinthor Bjarnason       Internet: stb at isbank.is
Islandsbanki h.f.         UUCP:     {mcsun,sunic,uunet}!isgate!isbank.is!stb
Kringlan 7                Phone:    354-1-608000
155 Reykjavik, Iceland    Fax:      354-1-679037