Yes, upgrade your mobile's firmware. Do this.. Uninstall Nokia PC Suite and NSU from your PC and restart it. Now download the latest version of Nokia PC Suite and NSU from Nokia website and install it in your PC and restart it again. Now turn off firewall and antivirus software and connect your mobile with PC. Now backup all the data of your mobile using Nokia PC Suite backup utility (for safety, if any problem persist). Now restart your mobile and connect it with your PC using original data cable. Now run NSU and do the procedure as written in NSU. Don't run any application in your PC or mobile. Don't touch your mobile untill "successful update" message appear in NSU. Good luck...
If you like my post then give me "Kudos" star...