bionic got the Xvid correct, download from _http://ffdshow.faireal.net/mirror/XviD/
Get the 2.70 pack from _http://scifi.pages.at/manolito/CCE270/D2S_CCE2.70.zip and READ the included text
Its said all better in there than I can ever explain
It also explains some of the nice things 2.70 can do over earlier versions.
The AC3 plugin has also been recently updated and now uses Aspen to do the ac3 conversion, not sure which one u got but hey, if its working
_http://nickspage.pwp.blueyonder.co.uk/ac3enc7+AC3_DVDAuthor.zip
And it should be made compulsory to use the Muxman authoring plugins as well, again from _http://www.megaupload.com/?d=XOD7JQTM but then bionic might have a later version that hes holding out on
Just as a comment, I have never closed GOPs, from how I read it, its a preferred option in DVD specs, not a compulsory option. I have always ignored DVD-Labs warning (its not an error) and has never created any playback issues.
The new TMPGEnc DVD Author ver 3 now allows the use of Subtitles and uses the *.str subs files, its working well for me