I have a BB 7310 with 507 error code after unsuccessful update of OS (connection died halfway). Tried several hours re-installing different versions of Device Manager and Desktop Manager, using different computers, etc.
Finally, success! The key thing is to use JL_Cmder software (download from this forum) to wipe the OS. It doesn't matter if Desktop Manager says device not connected before update.
507 error code DOES NOT mean the OS is wiped out. As soon as the WIPE command is used on JL_Cmder, my BB updated immediately.
Very, very happy