Try the online converter, if it's a web video. It really is about the best FLV converter. Once you have an MPEG4 or DIVX, conversion to MPEG2 for DVD will be simple enough.

I've converted a lot of low-framerate FLV vids and never had synch problems. Usually the trouble is poor video quality.

If you have a URL for the video, I'd be happy to play with it.