It didn't help something. I remember I had years ago the same problem, caused by GenTool. I had to change the Lan-IP in C&C zero Hour. Then it worked.
Can I change the Lan-IP in the options.ini ?
When I login to zero Hour Multiplayer the start screen, where you have to choose your country is coming for a sec, then comes the error. (here a picture: http://prntscr.com/e5b6lv )