Editor Software for FLV & MP4 files

I'm looking for a video editor (prefer freeware) that works with FLV & MP4 files. In some cases, I would want to save to Xvid (Avi) rather than FLV. I'm also looking for no quality loss (no rencoding?).

I've been using Avidemux for AVI and it's worked great, but can't seem to get the same results with FLV and MP4 files with it.

Would appreciate software recommendations.

Thanks..Johnbil