Hope this helps you: http://www.mpgh.net/forum/175-crossf...-messages.html
And if you're too lazy to read that... Here are the steps:
1. Uninstall the game completely. 2. Disable your antivirus completely. 3. Re-install Crossfire. 4. Re-activate your antivirus.
The reason this error occurs can be if you install Crossfire and your anti-virus program finds one or more of the files "dangerous."