1. disconect internet conection, do full erase without battery, disconect device. then insert batery and type "start" it will show no OS in devise, then remove batery.
2. flash your BB like in post one without batery, (make sure you have your internet conection enabled back again)
3. when it starts "Wait for device initalization" insert batery
Try with diferent OS for your operator, works 100%
Wish you luck