Multiplexing m2v and AC-3 file with TMPGEnc

[DarthJango]

I use DVDit to author and burn my DVDs and I usually have it convert the sound to Dolby Digital but it takes forever to do that on my computer so I thought I'd try to convert the sound to AC-3 using Soft Encode first because it coverts alot faster. I thought it would cut down the time it takes DVDit to convert and burn. Well I Demultiplexed the movie with TMPGEnc then I converted the mp2 file to wav using winamp then converted the wav file to AC-3 using SOft Encode. Well when I try to multiplex the AC-3 file and the m2v file together with TMPGEnc it won't do anything. The window will come up saying outputting at the top and will have the progress bar at the bottom but thats all it does. I have the AC-3 codec from the Nimo codec pack. Is there something else I need? I played the AC-3 file with PowerDVD and it worked fine.