need help in Netscape Messenger

i am using communicator 4.76 installed in a P3 w/ 128 MB ram. I've got more than 1k messages in my inbox. Suddenly my messenger prompt me an error message "Netscape has performed an illegal operation..." and i wasn't able to run it again. but when irename my inbox.snm in the \Program Files\Netscape\Users\...\mail subdir, my messgr. run smoothly. Is there any way i can recover or access my old inbox??