I have read all the answers relating to the "error has been
encountered and Outlook Express must close," or words to that effect. 
When I asked this question in a general Google inquiry, Microsoft
answered that since I was using Office 97, then an update to 2003
would cure this.  Do you believe this is true?

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Request for Question Clarification by tisme-ga on 09 Aug 2006 22:42 PDT

What operating system are you using?

It will be better if u update or trying doing an Online update for
office97 , that just might help u , the only problem is that buying an
office2003 key is expensive ....

No do not upgrade Office.
Upgrade your Internet Explorer to version 6 
get the high encryption key.

Possible defects -
It may be due to the encryption level. From 48 bit (1998) to 128+(2003)

It may be due to a virus or trojan. Make sure you are using an
uptodate virus program with the email plug-in turned on.

Some email you are recieving may be more secure than others, and when
it encounters higher security level. The msimn.exe [Outlook Express[
fails.

Corrupted Harddrive - bad sectors
Severly fragmented drive - Defrag Harddrive.
Insufficient Memory for the number of programs opened.
Swap file too small - If you need to increase size, defrag first,
change size, defrag again. (this method is better)