Alright!
I've just found the solution for me:
Code:
rtmpdump -r "rtmp://apasfw.apa.at/cms-worldwide/" -a "cms-worldwide/" -f "WIN 11,1,102,55" -W "http://tvthek.orf.at/flash/player/TVThekPlayer_9_ver18_1.swf" -p "http://tvthek.orf.at/programs/1003023-Winterzeit/episodes/3520863-Winterzeit/3520867-Aktuelle-Reportage" -y "mp4:2012-01-31_1740_tl_02_Winterzeit_Aktuelle-Reportage__3520863__o__0001045663__s3520867___ge_O RF2bHiRes_17404113P_17460404P_Q6A.mp4" -v -o mp4_2012-01-31_1740_tl_02_Winterzeit_Aktuelle-Reportage.flv
Simply adding the -v switch solves the problem.
The filesize now is also much smaller.