I actually have the same problem you have described. A more accurate description of my particular problem (just to make sure it is the same as yours) is:
When seeking (jumping timecodes) during WMV playback, when the video resumes from the new timecode, the video will temporarily speed up (it starts a few seconds behind the seeking point), while the audio properly aligns with the seeking point. When the video finally catches up with the audio, the playback resumes properly synchronized.
In my case, I found that the problem will only manifests itself in DirectShow-based media players (Windows Media Player, Media Player Classic, etc...). The only media player that I've used which does NOT have this problem is VLC Media Player, which uses completely self-contained codecs for playback.