Curve 8520 can't backup with device manager

[sindibade78]

hello, i have got an error msg :net rim bb messaging app (199) is not repsonding and uncaught expcetion : index 8>=8 .

I have trying to fixe it, before i need to do a backup with devise manager. when i try connect the bb to device manager and clik to backup, i got an error msg seen : can't do backup database. all mailing service on bb are not working and all mailboxes are deleted. the bb still freeze rondomlly.
please i idea to resolve this issue.

[kryptic123]

Try reinstalling DM then re installing the OS