Might try a Jl_Cmder wipe of the device.... It deletes EVERYTHING! DL and install Desktop Manager and the Handheld OS from your service provider... Then DL Jl_Cmder (it's in my sig) and wipe the device (backup or synce 1st ofcourse) then run Jl_Cmder and wipe the device.... It will boot to a white screen the open DM and install the OS using Application loader.... restore the backup or resync and all is good!
Also check and make sure the device is recognized in windows.... Start >> Right click on My Computer >> Device Manager and see if the BB is listed under devices...