As reported by our friend DMw, the link that he provided may have the answer I'm looking for (I haven't tried this as yet, but I reckon it may be a goer, although I'm wondering why I didn't think of it myself). The suggestion is to run the DVD folder through DVDShrink (without compression) and this may filter out whatever nasty bug is contained within. I'll give it a try soon and let you know whether Nero won't spit the dummy any longer (or not).

There was another suggestion of removing the VIDEO_TS.VOB file altogether, but I'd rather not risk that. Anyway, I'll let you know how it goes one way or another.