Well, very simple.
Firstly I flashed my EW822U to the B2I7P (DW800A firmware) using winDWFlash
Then I updated the B2I7 using mainly the firmware collection from the "Unofficial BenQ DVD ReWriter Firmware Page" in this order:
then I flashed the B3BC from DW822A
At this point I updated the firmaware as if I had the DW822A up to the B3LC
I don't know if it is possible to jump some of these steps...but in any case I followed all the procedure. The rationale is that the DW800 is the "father" of the DW822A/EW822U and the usb problem for the EW822U is only Benq "adhoc/false" problem.