two pass encoding fail

My last post was too euphoric too soon. WMEncoder is not allowing 2-pass encoding for some reason. When 2-pass is selected, it exits as soon as it finishes the first pass, and a 2 kB or something wmv file results. 1-pass is working, so using that as a workaround for the moment. Wonder if using avi files with ac3 audio is the culprit.