Has anyone tried to back up this movie?
It seems to have 8 different feature length tracks and I have tried twice now, the first time with just one of them and the second with all six - but each time I have ended up with no audio, although Clone has English 2 and 6 channel ticked off.
What gives?

This is very weird. I went back and made sure I selected anything with AC3/6 on it including all the Dolby and film company promos and bingo I have sound.
To elaborate, I deselected 12 of the 25 video titles in the options list in Clone - leaving 13 titles.
However, when I look at the finished ISO, it still has 25 titles, including a lot of 0:01 2 AC3/2 En titles that weren't there before.
Can anyone explain?

Finally its happened to someone else. Hidden Audio is a new trick I've come across with several of my titles.
Exactly, one of the only ways around is to clone the entire DVD crap and all. If you look at the Clone DVD list of tracks and titles, do you have some 0.0 in time yet labeled AC3/6? These seem to be the answer. When I backed up Once Upon a Time in Mexico I just did the title, it had no sound. So I did the whole thing, I got Sound. Then I just did the title again but selected all the 0.0 AC3/6, anything that was 0.0 in time but had Audio and Shazzam I got sound.

Not exactly.
I previewed all the bits and pices and only kicked out the stuff that was outakes or director's comments which was obvious from the footage.
Still can't understand why there were 8 feature length tracks (but I left them all in) and I left in all the short promo stuff as I said with AC3/6 on it - got it to about 83 per cent as I recall.
There was no 0.0 stuff so it must be a variation on a theme.