Hi Vlad,
I am new to AVS products but I can confirm that multipass is not working. The Converter tested is the newest (8.0.4.495) of today. I am evaluating your product to convert (2011 camera models of) Canon .mov files to either H.264/AVC or WMV9, and I am especially interested in best quality.
If the single pass default options have worked (with some better result with the WMV9) the multipass didn't. So I arrived to this thread and I can prove the issue reported by jcthomson.
I link here a 40 MB original clip from the camera (11 seconds):
https://docs.google.com/leaf?id=0BxK6VmqKqXslMmNiMTAyY2MtMTI5Zi00ZTM2LWIzNTUtNTVmODZmODhmMDhm&hl=en_GB
After running the first pass I got a 6.815 Kb file and the attached h264-1.pas (located in the c: root)
When running the second pass I get the message error, see the screenshot. I think is easily reproductible in your environment.
I also found a different issue on the window of the WMV9 configuration but I would rather open a new thread since the root cause is different (selected user values are not stored when clicking the OK button).
I like very much your product and also your efforts to answer the complains, is a key strategy to make good quality SW (I am SW developer and face the same challenges
Valentin