burnix2, be sure to add that very smart BenQ support person to your address book. We will have a lot of questions for them when U9 hits the fan.
That method is not always necessary, but it does prevent getting a bad flash.
It's wild that they would have you go through all of this trouble as their very first response. Wow.
That method is almost exactly what I had to do to get one of my drives to work right. Their firmwares are not "step" upgrades, but there seems to be some problem going from 1620 to 1620 Pro. It also happens when changing from P9 to T9, and possibly the reason that many people returned to P9 is because they couldn't get a good flash up to T9.
When the problem happens, it makes for big error spikes at the end of scans and poor dual layer writing/RW writing.
A nice shortcut to BenQ's method is to go from L9 (use it at L9), then directly to T9. But, BenQ's method seems to be more effective in combating the "bad flash" issue.
I wonder if the issue is manufacture date specific (hardware problem inside the drive) or if it is interference with/in the easily-irritated IDE interface (possibly caused by sub-optimal computer/environmentals)?
Anyway, that really inconvenient method will work. And, it works well. I've done it almost exactly as you've described it (did it weeks ago--great results).
I wonder what kludge method will be required to get U9 completely (perfectly) on? Sorry folks, I think I'm going to wait that one out (I'll not be the first one to try it).
I wish I had the E-mail of that BenQ support person. I would do my very best to translate my questions into French.
P.S. N9 was a regional release for your area supporting newly popular medias (at that time) that you could easily find in local retail stores.