You can do one of two things...
First before you even decided which to choice - Back up your contacts and such with your Device Manager
Then Choice:
1) Options>Security Options>General Settings *Press BB Button* *Click on Wipe Hanheld*
2) Click this link and upgrade to a new OS - Starts you from scratch and upgrades also.
http://www.blackberryforums.com/gene...ilanguage.html
Follow this word br word and you will be fine.
*Personaly I dont think #1 will fix the issue.