I have always been a great fan of Nero. Still am.
I have been running Nero 6.3.1.7, and have been able to burn 800MB discs to the max on both of my drives without any problem whatsoever.
Both drives have the latest firmware.
Since installing the trial version of 6.6.0.1 I have found that any attempt at overburning will cause the disc to be ejected prior to any attempt at writing data.
I am certain that the problem does only appear when using 6.6.0.1, and have been able to prove it by swapping back and forth from the two version of Nero.
Please note: There is another poster reporting precisely the same problem.
Please see: http://www.cdrlabs.com/phpBB/viewtopic.php?t=18073