If you've eliminated the drive itself, the media & the burning software then you have to start looking at other possible causes which unfortunately means you need to troubleshoot your entire system to find the problem ... start by doing a complete uninstall of all DVD-burning software on your PC, then manually delete all related directories & (if you feel comfortable doing so) registry keys, then re-install Nero only, patch to most current version & try again.
Other possible issues are corrupted/damaged Windows system files or a severely fragmented hard-drive ... run a full check-disk, then defrag your drives & try again ... worst-case you might find that you'll need to format & re-install Windows to fix the problem.
Edit: Since I see you are running Vista, my guess is you are correct about an update hosing things on you. I've actually had Vista chipset driver updates cause all kinds of problems on my primary PC including having a software RAID array damaged & losing the ability to burn any type of optical disk ... recently I've gone back to XP Pro for just about everthing.