http://www.benq.com -click on "global" from the site map -click on support from there, track down and download the firmware for your drive
It is a windows installer. Have no disc in the drive during use.
Compare scans of your media with scans listed on the scan page.
scan tool located at
http://www.cdspeed2000.com and you're looking for cd/dvd speed
If you get results inconsistent with the rest of us, try flashing the firmware again, check cables, IDE drivers, virus scanner, etc. . .
Some people report that a bad flash can be corrected by returning the drive to K or L firmware before "upgrading" once again. This does work. So does the "official" method of simply flashing again with the same firmware until it works. Eleven times for me, and it finally worked as expected. The unofficial method was much faster.
Now. . .the rest of the story: Environmentals such as software, services, power supply, vibration, and more can cause the 1620pro flashers to misbehave.
So, you might want to burn a few discs and make a few scans in "as shipped" condition. That way you can tell if your flash update worked correctly.