I seem to have a different variant of the DVD+R close problem to other people here.
I'm using a Pioneer 106D, 1.08rev drive with Nero 220.127.116.11, using TDK DVD+R 4x media.
When selecting "disc at once" mode I get no errors on burn completion - in fact, it even completes verification with no errors reported!
But the discs are not closed, the data on them is unreadable, and Nero also can't close them through "disc information" - it writes a second, unclosed session on the end of the disc and then aborts the finalisation process at 50%, ejecting the disc.
I have burned about 25 DVDR discs before discovering this problem, and since verification completed fine every single time, I've deleted the original source material I burned.
Any ideas, anyone?