What software are you using for burning?
I can't really help, but I can sympathize.
I have very similar situation -- on a 4-year-old computer, with a 4+year-old HL-DT-ST dvdram GMA 4020B. It stopped making readable discs about the middle of December. Due to its age, I guessed that its laser was failing. (All of this is at home, of course. WinXP Home, SP2)
The burning process itself seemed flawless, no problem reported; I use Roxio EMC version7. (I've been using Roxio and its Adaptec ECDC predecessor for 10 years.)
Just before Christmas, CompUSA had a sale on a Connect Computers' brand of burner, sale price of US$7.88!!! (after rebates). I finally received mine yesterday. The stickers and everything said HL-DT-ST dvdram GSA H10N.
SAME RESULT!! The burning is fine (apparently) but nothing can read it, and (using rewritable media) it has to be erased before I can write anything (i.e., nothing) on it again.
Are you using Roxio? If not, then what are you burniing with?
I called in our PC Support -- my daughter (really -- she works PC Support at a Lab at the local air force base.)
I don't do automatic Windows updates. She installed an update to the Windows updater, nothing more.
Then she used WinMedia Player v10 to try to burn some musical tracks. It Worked! But Roxio (the Creator Classic program) will not really burn.
That 's not any help, I know, but I'll address the same issue to the Roxio forum tomorrow night or Friday.