Ive used nero vision for a long time without almost any problems, but lately its just been really annoying. Out of nowhere. When i try to burn PAL it asks if i want it encoded in PAL, or NTSC, I choose NTSC, here's an image: http://i42.tinypic.com/dqkh29.jpg. Then i press burn and i get an error, it says: unable to prepare data for recording... here's another image: http://i42.tinypic.com/2gu0i1g.jpg. If im burning something that is not PAL it will transcode, but will not accept any DVD i put into the drive, it keeps saying that there is not enough space on any of them. Nero Vision always worked for me, i dont understand why it became so buggy.
When I had problems with Nero acting up, I would uninstall it using the Nero Clean Tool and reinstall. Note that the link applies to Nero 7 and you must note your serial number(s) before uninstalling/reinstalling. http://www.nero.com/enu/support-nero7-tools-utilities.html
Can you save the output from Nero to the hard drive (elect not to burn the files) then use the likes of ImgBurn to burn the DVD. Separate the two functions to see if it's a Nero problem or a burner problem.