OK... it seems it is a problem occured by a german provider.
See:
http://dayzmod.com/forum/showthread.php?tid=13817&page=1
http://foren.t-online.de/foren/read/service/dsl-festnetz/internet-performance/hat-die-telekom-bestimmte-seiten-ports-gesperrt,790,9848301.html
Greetz