If you want to make absolutely sure, you can try these steps:
- uninstall Demigod completely
- delete the Demigod folder in your My Games directory
- close Impulse and execute this registry key: http://forums.demigodthegame.com/373670/get;2506128
- reinstall Demigod
- start Demigod as Administrator and log into online Multiplayer
Alternatively try step 2, 3 and 5 first, without uninstalling Demigod, if you don't want to go through that.