Dvd burning trouble with my liteon ldw-411s

ok im new here so go easy on me. i have recently had big trouble burning dvds… i have and are using liteon 411s,windows xp,celloron 2.6,dvd xcopy,ritech dvd-r,liteons newst firmware fsoj. i have burned about 40 or so dvds with no trouble at all,then i had acouple of coasters so i went with the latest firmware and it has got worse since. i have done the things dvdxcopy recomends as far the black list disabled mcafee,roxio,and all the startup stuff. what it does is when using dvdxcopy it works fine all the way to were it is finalizing the disc.then its almost like it starts burning agian it turns the red lite back on the drive and keeps going.xcopy says it is still finallizing.then the burner will still keep runing for about as long as anormal burn would take. and if u let it go after awile it will eject and say burn completed sucsessfully.but it will not play or be even recognized by anything. i have swithed software, reloaded or flashed firmware about 3 times.inow have a stack of about 10 coasters. i even took my discs to buddies to make sure it wasnt a bad batch or something and they burned fine.any help would be great thanks.