Burning Cd's In Iphoto


I'm getting a "medium write error" when trying to burn photos from iphoto. (I have a new g4 ibook with a super-drive) Normally I just select a bunch of photos in the library screen, go to share, then hit burn and voila! but now it will eject the CD after about 5 minutes of "pretending" to burn. I'm not using crud CD's and it was working just fine two days ago! Greg from Apple tech support ran me through Go--> Home--> Library--> Preferences to remove potentially corrupted files and it worked great; once. Arrggh. Also if I create a new user and burn from there it works OK. Maybe I should just do that.