Sounds like you have memory issues. Check and post your available memory here (options > about)

Pull the battery (with the device on) and then check again and post.

If it seems to be low on memory, try some of these links:

Why is my 8100 Pearl losing its call logs or message logs? - BlackBerryFAQ

How can I free up memory on my 8100? - BlackBerryFAQ

http://www.blackberryforums.com/gene...ee-memory.html

http://www.blackberryforums.com/gene...-logs-sms.html

Additional information on memory leaks on the 8100 - BlackBerryFAQ

Good luck