Can you flash your drive with the normal BenQ firmware(i.e D.UC)? Try upgrading firmware W/ newer Benq version before flashing K.RC, this will verify that your drive can be flashed.
If so, I can step you through the method that I used to flash my drive, it seemed to work flawlessly. I have also heard of people having problems flashing with 2 drives connected on the same channel, although I have a Pioneer DVD-ROM set as master and BenQ CDRW as slave on secondary IDE channel and it worked fine. I have seen firmware updates that ask you to make sure you do not have a disk in the drive and that the drive is closed before updating. IMHO if you want to try a safe method for flashing your drive, make sure it is the only one connected to your IDE channel(if secondary), if its on the primary w/ your hard drive then obviously you don't want to disconnect it unless you boot from DOS boot disk and flash from DOS. What utility are you using to flash and how? I used MtkWinFlash 184.108.40.206 in ATAPI mode. Is it possible you have the other 482448 model or is firmware D.XC?, or flash utility is trying to flash wrong drive, could bin file be corrrupted?(doubtful, but you never know, BTW the size of the kRC.bin file I used (from cptsnoopy) was 512 KB.
Hope this helps,
It's all in the reflexes..