The error you mentioned above can often occur due to various reasons but one solution is to remove the current OS and by auto loading the OS again on the device.
Download the autoloader for your device from here
http://developer.blackberry.com/
And follow the steps below:-
1-turn off your device
2-connect your device to pc
The downloaded autoloader must be present on your pc and installed or unzipped
3-now run the autoloader and turn on your device.
Once autoloader recognizes your device it will start loading OS on it again after its finished green LED will light up.
After its finished your phone will restart give it sometime and all done.
I hope this helps! Good luck!