I and many others are having the same problem. I couldn't play online so after trying every .exe and .dat file I could, I managed to get it to work online.
Patch the game to v1.05 and make sure all files are the originals.
download the link below,
http://dl.gamecopyworld.com/dl.cgi?dev-ccg!rar
Extract ONLY the "generals.exe" file into your directory. Remember that, you only replace the .exe file, NOT the .dat file.
You should now be able to play online normally, but that is if you have a real cd key.
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