Zune Playback Problems

I've been using WinAvi to convert my DVDs to .wmv for playback on my Zune, but it seems that about 50% of the movies that I convert do not playback properly. The main issue is that the audio does not sync up with the video, I can see someone's mouth moving but no words, and then I hear the words a few seconds later. I've bypassed this by first converting the videos to .mp4 using handbreak, and then letting the Zune software convert the video to .wmv when I being the sync process. However, this method is much more time consuming, and it also causes a loss in video quality. Does anyone know why this is happening or what settings I should have WinAvi on so it does not cause this problem anymore?

Thanks