ffmpeg audio sync

[Camilo Reyes <camiloreyes82%yahoo.com@localhost>]

Hell All, I'm trying to convert an mpeg-1 file into a smaller version of
that same file. All I'm doing in ffmpeg is changing the video and audio
bitrates with something like this:

  ffmpeg -i <in-file> -r 29.97 -b 500 -ar 44100 -ab 128 <out-file>.

The resulting file unfortunately is out-of-sync and I can't figure out
what else I should be doing to it. Anyone experienced a similar problem?
Should I be using somethig else? Thnx.