Thanks for the info MysticEyes, I tried all that but so far still no luck.
I continue to experiment and so far, it seems to be just one video file that's causing all the trouble - I tried a different project with anoter Mpeg2 video, and it worked, so now I'm transcoding that video into an AVI, see if that helps, and I'm also going to put the same version of Nero onto a 2nd machine, virgin installation, to see if the same project works on it.
The only thing I haven't done yet on my main PC is to uninstall Nero altogether, use that Neroclean tool and reinstall.
If neither of the above work, can you recommend an alternartive DVD-Video burning suite that would do the same job? (e.g. take 640*480 Mpeg 2 videos, make a simple menu, transcode the lot to a DVD video structure and burn to DVD/Video)?
I'm trying to migrate a bunch of VHSes to DVD and this is a major PITA.