I got the same Plexdrive and here the 12x recording works just fine with Nero 4083. My SCSI card is a Tekram DC395U, I even didn’t have to install any windows drivers!
I saw the reboot problem once before with a CDRom reader. After searching for 8 hours I concluded that the drive must be broken. So I went back to the shop, got a new one and that one just worked fine!
Did you look at the settings of your SCSI card (adress, irq, dma etc…??). Did you look wether your motherboard’s bios needs changes?
About the message “No bios installed”: don’t worry, this message is normal! It means that there isn’t any harddisk connected to your SCSI adapter.
Greetzzzzzzz and good luck!