That error actually is related to things that have wrong version of entities or mods.... you have no mods loaded? or have you ever modded your game or edited game files?
Make sure you have the right patch. If you have non GOTY version of the game then u get this
http://www.1cfiles.com/MoWAS_patch/m...05.13-full.zip
If you have GOTY version of the game then you get this
http://www.1cfiles.com/MoWAS_patch/m...en-2.05.13.zip
Also if you ever used steam or can use it you can register your game with steam in most cases using the gamespy cd key that came with your game, through steam game would update and verify itself automatically.
Make sure you have no mods loaded, reboot, if that doesnt help uninstall the game and manually check the files are all gone(directory where the game files were). Then reinstall the game and apply proper patch.