I have a similar problem. I **HAVE TO** use DOSFLASH16 to flash my drives. My Motherboard has am Intel chipset and NO IDE ports( JUST PCI-E 16x and PCI-E 1x.) this means I CANNOT install a VIA Sata expansion card into my computer. I have tried to use Jungleflasher numerous amounts of times and it will simple not see my DVD drive. Under "Device Properties" it ALWAYS stays at "No drive Detected,(Tried a Liteon, 2 Benq's, and a Samsung)
But fortunately with a BenQ you can do it through dosflash EASILY.
You need to make a USB drive to boot from. In my bios I have to set me Sata drives to ATA, not the other (default) mode, forgot the name.
1. Turn computer on, followed by 360, almost directly after.(I'm connecting my DVD drive to SATA on the comp and powering it with the 360)
2. Once at the cmd prompt just type "dosflash". WITHOUT the " and ".
3. Press the number corresponding to your drive(Mine is usually 1, if I keep my HDD plugged in.)
Somewhere along the line it will ask you to either r(read) , W(write), or e(erase). Press r when it asks.
Save the file as orig.bin (or whatever)
Then reboot to windows...
Open up Firmware Toolbox (I use .4.

Load the orig.bin you just saved and copy your key.
then open the new benq hacked firmware 1.51 or 1.6 whatever is out I don't remember exactly. replace the key with the one you just copied.
Click on save key, save it as whatever you want onto your USB drive you use to boot with, something easy( I use hacked.bin)
reboot and turn your power on to your dvd drive a second or so after your computer turns on.
once in dos dos and type in dosflash and choose your DVD drive number(usually either 0 or 1 depends on what is hooked up, if you have a problem unhook everything SATA, even your HDD(except your 360 DVD drive of course...)
This time around choose w(for write) and type in hacked.bin(or whatever you named it).
After it is done, turn off the computer and power down your 360. Might need to power cycle it 1 extra time.
After this your Benq should be flashed!

rebo