I could not join multi-player games as I said my Serial code was in use. So I went to my Crysis 2 directory ( Eg.. C:\Program Files (x86)\Electronic Arts\Crytek\Crysis 2\bin32 ) and right click on the Crysis2Launcher.exe and Crysis2.exe and set them to run as administrator.

After that she works fine in multi-player.

Im running windows 7.

This doesn't work...