thx vpaulus and tarrak! I've located the problem in the meanwhile. The firewall of my router (didn't even know that my router has one....embarrassing) was to blame. I disabled it and now it works fine.

my games has been also updated with the newest patch (v.1.13). I deactivated the firewalls, I reinstalled the games, the internet is ok, other games runs without problems (even over steam for example) but ..... the upload error always exists (with one exeption). both pc runs on win 7, 64 bit. the co...

It's seems that the multiplayer connection/upload problem still exists?! I have tried to play a MP with a friend last week and today --> connection with server failed. sometimes it happened when we wanted try to create a scenario, but always the error appeared when we wanted to upload our turns. I b...