Error Message when closing Outlook

I am running Office XP on a system running Win XP Pro
with 512MB of RAM and an AMD XP 1800+ CPU. I have the
latest service packs and patches for Office and XP.
Every time I close Outlook, I get the following error
message:

OUTLOOK.EXE - Application Error

The instruction at "0x6601cd49" referenced memory
at "0x000000a0". The memory could not be "read". Click
on OK to terminate the program.

I had this error before I upgraded my RAM and motherboard
and after I upgraded. I do not get this error with any
other program. Does anyone have any idea what this is
and how I can eliminate it?

Thanks

Mark