What’s your video source (.avi/.wmv or others) and size (height/width) when converting with SMC that syncs the video and audio real well?
I usually use mencoder to encode everything to 20fps 224x176 mpeg4 plus 128kbps cbr mp3 and drop that to SMC, as the first step can be done unattended from a script. I never saw gross a/v offset in the result produced this way, but SMC hangs perhaps 1/3 of the time (which does not have anything to do with your question).
I tried everything, everything gets out of sync 
, only way for me to avoid that is split all the movies into 10-15 min clips.
The only way I’ve done it is through another converter first. Then SMC. I use anydvdconverter.
Video
codec: xvid
Size: 320x240
bitrate: 768
Audio
Codec: mp3
bitrate: 128
And then I make sure the output is in English.
