You can try this:
Install BlackBerry Desktop Software to your computer. If you don't have it you can get it from
www.blackberry.com/desktopOnce installed open it, connect your BB to it and go up to Device and select "Delete data."
Under Delete Device Data click the radio button for "Selected Data." The list of databases should become available.
Scroll down and select BlackBerry Messenger.
Uncheck the option to Backup data before deleting.
Finish the process to remove the data for BlackBerry Messenger.
Disconnect the device. Make sure you're connected to a wifi network or cellular network and make sure that you have the BB logo up in the upper right corner near your signal strength. If you have no BB Logo contact your carrier.
If you have a BB Logo then try to login to BBM again.
This all assumes that you have a BlackBerry ID already set up. You can go to
www.bbid.com and make sure that your BBID login credentials are valid.
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