When I try to encode two audio tracks, both ac3->mp3, the first one is encoded ok, and the other one causes an error in Besweet. It doesn't happen when I oncode them separately. Any idea why?

I usually use external apps for encoding the secondary tracks, but this is just annoying.

Not sure to be honest, but I prefer releasing audios as bonuses as not to compromise the rip quality so don't tend to do it that way. If you use MPC you can play unmuxed audio streams just as simply as muxed ones.

When I have done dual, league of gentlemen for example, it didn't put up much fuss. You have to make sure you setup the second tab correctly, add in the audio and check all the relevant overhead, and dual audio stream options. Then it encodes fine.

I did have a problem a while back, but i solved that by just doing a besweet encode and muxing afterwards in virtual dub mod.

That's what I always did and am still doing, I was just curious.

I on the contrary prefer releasing them muxed, because otherwise all the additional mp3 tracks dry up very quickly. Many times I tried to download separate commentaries of which only a few chunks were available. I always look at picture quality though, checking whether it is not too low.