Sounds like she's dead, Jim. You might try reflashing your drive to earlier frimware B7L9 which is rumored to reset the drive.
Otherwise, it could be your drive is being recognized as a DVD-ROM instead of a DVD-R/W. Go into Control Panel--->System--->Hardware--->Device manager--->DVD/CD-Rom drives and select "uninstall" for the BenQ 1620. Reboot your system, and it will reinstall the drive.