I got this problem for a while, but the solution is actually pretty simple!
Create 2 new folders named:
VIDEO_TS (and) AUDIO_TS
Place ALL your initial created files (.vobs,.ifo's,.bup's etc) in the VIDEO_TS folder. Leave the AUDIO_TS folder completely empty.
So when adding folders in nero, click and drag to select both folders in the window to add them. And voila! compliance fine.
Basically dvd players look for these two files on the DVD when loaded. U may find that ur previous 'non-compliant' DVD works anyway if u have a friendly DVD player.
This should do the trick