AFter following some tips on extracting the audio from my avi in virtualdubmod, and having a new ac3 file, i open tmpgenc and i go to the mpeg tools and simple multiplex, after i choose my video and than select my audio i get an error saying illegal mpeg audio stream, well the first file i did has the exact same properties according to avicodec, i followed the exact same procedure doing the 2nd file, but its giving me errors.

audio is

448kbps, 48000hz, 5 channels. 0x2000 = ac3 dvm, supported

the first audio file that worked fine was the same??