Originally Posted by NJBlackBerry
How much free memory do you have (Options / Status) will tell you.
If it is below 12-15mb that's the reason why messages are being deleted.
I don't have memory in Options > Status, but like I said in my original post, I have plenty of file free space:
File Free Space: 125589168 bytes
In Options > Memory, I have 119.8 MB of Free Space for "Application Memory". I have 1.7GB out of 1.8GB free on my memory card as well.
One other thing is when my handheld is doing this, if I manage to read the messages on my handheld, it won't reconcile with my mailbox. They'll still be unread on the server.