Had same problems here so i’m going to post my situation hoping someone else has benefit of it.
I bought a S203B drive also, installed it on a promise PCI controller card with an extra HDD i had spare.
After burning a few discs (5x) and watching the latest disc i burned (max speed verbatim) it was acting strange and skipping whole the time in standalone dvd player.
So i burned it over at 8x, but burned layer didn’t looked well imo but played fine now (light and dark circle’s, my previous plextor had the same changed it 3 times).
So i decided to flash it to B03, downloaded FW flashed it, reboot and gone was drive and flash bank said BOOT.
Flashing it again maybe something went wrong but everything went fine before, still BOOT.
Flashing again but then with B02, still BOOT
Disconnected all S-ATA drives i have in system except OS that is S-ATA also, burner still on PCI controller and OS on main S-ATA port.
Flashing again still BOOT (now i was getting pissed off)
Again with lower FW and still the same.
Picked different cable and flashing again, still nothing.
Booted in save mode, flashing again, nothing.
Checked wires and decided to plug in drive next to OS drive on dedicated S-ATA port ( not on my asus p4c deluxe onboard promise controller what it was 1 step back)
Booted system, noticed new hardware ( i thought i was lucky) still BOOT
Flashed it 1 more time before i was going to trash drive and voila it finaly worked with B03.
Short version from above is imo that the S203B doesn’t like it to be flashed when it’s connected to controller card instead of real S-ATA port. I have no RAID settings, all is configured as IDE
-update- This is the first time i have such trouble getting FW upgraded, is that normal behavior for S-ATA drives, because IDE’s went like a charm against my S-ATA experience.