This one should do the trick...
Code:
rtmpdump -r "rtmp://flash51.xo.tcdn.ustream.tv:1935/ustreamCdn/flash57/2298576" -a "ustreamCdn/flash57/2298576" -f "WIN 11,5,502,146" -W "http://static-cdn1.ustream.tv/swf/live/viewer.rsl:369.swf" -p "http://www.ustream.tv/ffrc" -y "streams/live_1" -o "some_cats_here.flv
Accidentally deleted my previous post here.