I've heard a person say that after the messaging app force closed, all of their messages were erased. Are you using any Task Killers/Managers that may have closed Messaging?
Hasn't happened to me. My messages are safe and sound. And no, there is no auto-erase as I actually WANT this and unfortunately to no avail.
I am using the built in Htc/adroid apps.
I do have antivirus from the market but don't think I had it the first time it happened not sure. I may delete it.
uninstalled antivirus, hope this works.