If you go to:
Programs\Common files\Research in Motion\apploader
now, open a dos command prompt.
drag and drop the "loader.exe" application in to the cmd-window (does not work with Vista !) and, add /nojvm + hit ENTER
or execute:
Code:
C:\Program Files\Common Files\Research In Motion\AppLoader\Loader.exe /nojvm
This should erase the phone completely before loading the OS.
Load a firmware.
After that restore your backup.