Communicator deletes email from Inbox?

Recently, I have gotten two reports of email disappearing from Netscape Communicator's Inbox:

Bob Shalit writes: "Communicator 4.04.1 frequently completely deletes mail from the Inbox when I move to another folder, like the Send Mail or the Trash. I'm not doing anything at all, just leaving it in the Inbox. I come back, and its gone - not even moved to the Trash folder, just gone."

Sal Orlando situation involved having two different versions of Communicator in use: "I've been using Communicator 4.03 for quite a while and I use it for all my email. Recently I decided to give 4.05 a try, but also kept 4.03 around. There are some differences between the way 4.03 and 4.05 handle email - each time you open mail in 4.03 and then go back to 4.05, your preference settings for the mail window are reset, for example. Anyway, today I noticed that a week of email was missing from my Inbox!!! Completely gone. This seems to have been caused by switching back and forth between the two different versions of Communicator, and checking email in both versions."