|Thank you both for replies.|
not completely sure how to do the boot to live cd, but i guess i will look into it. Since it occurs to either drive and started happening at the same time, it doesn't appear to be a hardware issue.
When I back up a disk, I just have the source disk in one drive, and the blank to be burned in the other drive. Saves the little step of opening the drive and replacing with a blank. One is LG DVD burner, other Lite-On Blu-Ray burner. These have worked fine together for nearly 10 months. However, instinctively, I agree with you that it almost "feels" like some kind of "contention" issue, but I wouldn't know how to diagnose or fix.
Again though, weirdly enough, if I reboot they work fine until I replace the disk, then if I reboot it will be OK most times.
Thx for help guys, I appreciate it.