Illegal Operation when shutting Outlook

[geoffm]

Every time I close Outlook I get an "Illegal operation" notice with the following setails

"OUTLOOK executed an invalid instruction in
module <unknown> at 0000:00ff2a22.
Registers:
EAX=00000000 CS=02af EIP=00ff2a22 EFLGS=00010297
EBX=00ff0b50 SS=02b7 ESP=0056fc3c EBP=0056fc78
ECX=00ff0b50 DS=02b7 ESI=0056fc6c FS=400f
EDX=00000000 ES=02b7 EDI=00ff2a20 GS=0000
Bytes at CS:EIP:
8e 30 00 00 00 00 d8 0b ff 00 9a 79 00 00 30 00
Stack dump:
00ff2a20 00ff0bf4 00ff0b50 04001097 00ff2a20 00078300 00000000 00000000 00000000 00000000 00000000 00000000 00000220 00000011 00000000 00000000

Anyone have any idea what could be causing this?

Thanks