Lost my CD/DVD Drives

I have had Vista Ultimate installed for about a month. I have 2 CD/DVD drives
- one is USB, the other is IDE. Both have been working fine... until last
night. I can no longer see them in windows. Device Manager says the drivers
are OK, but Windows had a problem loading them (error 39).

I can see them when I boot up (before Windows starts). I know this because I
can interrupt the boot sequence and boot from either CD drive.

As I said, these have been working fine. No new hardware or software has
been added.

Thanks,
Ron