Ok - I am not the best at this but what exactly are you trying to do ? I would guess that "Medium Not Present" means that there is no disc in your drive...... thats when I have seen that message, either that or your drive is playing silly buggers.
Did the BenQ drive come with that firmware - BSMB ? I checked at www.rpc1.org and couldn't see that one - check the link below,
http://forum.rpc1.org/dl_firmware.php?download_id=2053
Perhaps if you confirm what your doing, for instance, trying to write an ISO image to a blank disc etc it might be a little clearer....