812 drive not accessible but 1633 has no problems

I have a lite on 812 and a 1633.
After installing the latest update of nero (I think it was working before that although I don’t remember the last time I used it) my 812 gives the error message of drive not accessible-incorrect function.
The 1633 works fine.
I have uninstalled and reinstalled all dvd related programs from my computer without any success.
I have updated the firmware on the drive. I have reversed it, used mtkflash in dos to change it back, updated it again (don’t think its a firmware problem but I don’t know).
I have XP SP2 and the drive is recognized in device manager.
I have tried cds, installation program DVDs, various r and rw DVDs.
When empty it tells me that nothing is in the drive.
When inserted, it tells me that it is not accessible.
Really confused and wondering if someone can help me.
Seems really strange that one dvd would work and not the other, but, I seem to mess these things up every once in a while without understanding what I might have done.

Have you tried removing the 1633S and switching the 812S from master to slave or slave to master, depending on your configuration. Make sure your drive is flashed with the firmware that you want to continue with first, by using the firmware on my site. You shouldn’t have to use MTKFlash unless the drive is not showing up in the BIOS or Windows. Also make sure the IDE cable is OK.

Sorry, i didn’t get an email showing a reply.
I guess this is the wrong place to be because i have been able to determine that a device called 1394 net adapter #2 will go to an exclamation point and the 812 will quit working. the 1633 continues to operate. i try to uninstall and whatever and it stays at an exclamation point. then it just pops back ok after a few days and the 812 starts working again. i have searched the net for info on this device and can’t find any real info on why it would quit. it may be my firewire but i don’t use it often and am never using it when it goes on the blink. i also have a toshiba modem for broadband in the same category that doesn’t ever go out. i can’t figure out what causes it or how to make it stop blowing up. i guess i will just have to live with it. doesn’t make sense that it would affect one dvd and not the other or that it would affect it at all.