There is no problem:
Code:
rtmpdump -v -r "rtmp://cp89928.live.edgefcs.net:1935/live" -a "l
ive" -W "http://tv.economico.pt/AkamaiFlashPlayer
2.swf" -y "EconomicoTV_MBR_750@19075" -o test.flv
RTMPDump v2.4 GIT-2011-12-22 (Compiled by KSV)
(c) 2010 Andrej Stepanchuk, Howard Chu, The Flvstreamer Team; license: GPL
Connecting ...
INFO: Connected...
Starting Live Stream
INFO: Metadata:
INFO: width 512.00
INFO: height 288.00
INFO: framerate 25.00
INFO: videocodecid 7.00
INFO: videodatarate 700.00
INFO: audiodatarate 64.00
26.349 kB / 0.00 sec
have you tried latest version of rtmpdump(22/12/11)?