3gp to theora problems again

hello.

as many times before i ran into troubles to encode
with ffmpeg2theora from a 3gp file.

the example files are here:

original: http://startx.plentyfact.org/media/theorastuff/test.3gp
ffmpeg2theora: http://startx.plentyfact.org/media/theorastuff/test.ogv

the 3gp file ( from some phone ) is 
  Video: mpeg4, yuv420p, 800x480 [PAR 1:1 DAR 5:3],
             2962 kb/s, 23.95 fps, 60 tbr, 1k tbn, 60 tbc Stream
  Audio: amrnb, 8000 Hz, 1 channels, flt, 12 kb/s

as you can see in firefox the video plays a bit like stop motion,
my vlc ( on debian squeeze ) won't play the ogv.

i am using

ffmpeg2theora 0.27 - Xiph.Org libtheora 1.1 20090822 (Thusnelda)

any idea what could be done about this?

startx