Double Shut Down Problem (DSDP)--The Final Chapter (for me!)

After several hours of testing last night and a zillion emails, I am at a stopping point on the DSDP issue. Mac OS 8.1 combined with Netscape Communicator 4.0.4 and 4.0.4.1 Messenger (emailer) causes the DSDP on my 9600, 8500 and 3400c. Neither cause DSDP on my PowerBase--to my pleasant surprise the much accursed Alchemy board is not cursed with DSDP.

I never get DSDP on any of these computers if I go online with Netscape Communicator 4.0.4 or 4.0.4.1 and do not use Messenger. I almost always, but not always, get DSDP when I send email or receive email with Messenger. DSDP is reduced somewhat on the 3400c by selecting the "New Message" icon on the Message Center but it nearly always occurs when using the "New" command from the Message menu. I have no idea why DSDP occurs intermittently because I followed exactly the same steps repeatedly, including the very same letters typed into the test email.