rtpmsink for justin / ustream

[puredata at 11h11.com]

Hi,

I am trying to use gstreamer to stream to justin.tv or ustream.tv:

gst-launch-0.10 -v videotestsrc ! videorate ! ffmpegcolorspace !  
x264enc ! flvmux streamable=true ! queue ! rtmpsink  
location="rtmp://live.ustin.tv/app/live_mykey"

but it's not working (no stream are send). with ffmpeg i can stream to  
justin with this cmdline:

ffmpeg -f x11grab -s 1360x768 -r 30 -i :0.0  -ab 96k     -f alsa -ac 2  
-i pulse -vcodec libx264 -crf 30 -vpre "medium" -s "1280x720"      
-acodec libmp3lame -ar 44100 -threads 8     -f flv  
rtmp://live.justin.tv/app/live_mykey

Anyone successfully used gstreamer with rtmpsink with justin / ustream  
or any similar service?

Thanks