1.Run Loader.exe (C:\Program Files\Common Files\Research In Motion\AppLoader)
Plug USB to Blackberry, then appear Unknown PIN, make quick press Next...
now you can upgrade your blackberry...
don't forget use full battery..
2.You need two files to get it to "no application"
Execute as follows:
loader -u load MFI-19441-023
Then you should be able to run desktop manager to re-install the OS.
Or this solutions,,
try Download loader.bat or loader.exe from 4shared.com
example : Loader-8520.exe
connect ur device
wait to view minutes
Then you should be able to run desktop manager to re-install the OS/upgrade.
thx by mangwie