Just because B follows A without any intervening activity, don't presume that A caused B.
The night of the Daylight Saving Time switch my computer shut down. That is, when I checked it in the morning, it had turned itself off. Mysterious. It has never turned itself off before. When I restarted it, the BIOS no longer detected my CD-ROM drive. It was OBVIOUS that something having to do with the Daylight Saving switch had caused the power-down and the loss of the CD-ROM. OBVIOUS.
So I don't check the basics. Whether it's all cabled up correctly. After all I didn't open the case overnight. What could have changed? Instead I try to reset the CMOS (i.e. BIOS). I download and install a NEW bios. I fiddle with it until I'm convinced the drive somehow blew up during the night, so I disable it in the BIOS and leave it at that.
For a while.
But I get to wondering. Maybe I should learn how to swap out the drive. I don't want it broken, because sometimes I want to boot from CD. So I open the case and examine the fixtures and the cabling. Nothing surprising, except that the CD cable is a transparent flat orange plastic ribbon cable instead of the usual multi-wire in gray ribbon cable of the type that is hooked up to the hard drive. Curious, I touch the orange ribbon and THE CONNECTOR POPS OFF OF THE CD-ROM DRIVE! How long it had been cocked to within a hair of coming off, I don't know, but overnight it must have vibrated just enough to become disconnected.
Plugged the connector back in and everything worked fine.
Lesson: Test those untested assumptions, bucko.