Complete BlackBerry Secrets Blog

This're that happen :
- The screen remains blank
- LED Lights On - Off many times .... red LED for about 5 seconds, and die about 2-3 seconds
- Can't get connected to PC via USB, you'll hear the notorious sound of connected and disconnected USB device in tune with the LED

This condition is called the "Nuked" Blackberry.

How to fix it :
1. Connect Blackberry to PC via USB
2. install the Blackberry OS, try with ver 4.5 first- if there's no results, download and install version 4.2 (based on experience) - Do not forget to delete Vendor.xml
3. Run Desktop Manager
4. Click the App Loader - Start
5. Wait until "USB-PIN: UNKNOWN" appears... click Next right away ... if you missed it just wait till it appear again.
6. Then continue the process as install / upgrade OS.

If you're success here, congratulations
but if you got error 507, do this
Turn off Desktop Manager... then repeat the process from no. 3 ... and this time the PIN should've recognized. If not ...reinstall Desktop Manager with the Repair option.

Run the process till Blackberry run normally with ver 4.2, then upgrade it to 4.5.

Related :
How to Upgrade / Reinstall BlackBerry OS