Wow, hard to believe the Power Supply was the cause of the problem but if it's fixed I guess you can't complain to much (other than having to shell out another $30 for a good Power Supply, hehe...). I'm just glad you got it switched out before it did anything more detrimental to the computer other than making some coasters.
I'd imagine it's hard for Optical Drive manufacturers to pin-point one thing in the computer and said that is bad or this is bad with so many variables from software to hardware to whatever. I can't blame LG for replacing the drive, honestly, and it was good of them to do so regardless if the drive wasn't bad or not - hopefully the new drive is working just as well as the old one did. Never know, if they didn't find anything wrong with your old drive maybe they sent the old one back? hehe
The power supply certainly was a good find! I'll have to keep that in mind if I ever have issues with DVD-Burning stuff that wasn't there before, nice to have a 400-Watt PSU laying around when you need it at any rate. Great first couple of posts, Lobster, hopefully you'll stick around and join in on some of the other forums.