I used to have the same problem but finally got hold of Aspyr, and they found a way to fix it .. By not if it works because I have not had time to try .. but it should ...
Message from aspyr...
Thank you for contacting Aspyr Tech Support!
This error has only been observed when the game is installed when anti-virus and firewall (Windows and 3rd party) settings are activated. Please uninstall the game and deactivate these settings (ie., AVG, Avira, ZoneAlarm). Double check your 'Processes' tab on your Task Manager.
Then click on Start --> Run and typing %temp%. When the window opens, delete as many of the files in that folder as you can.
Then reinstall the game.
Feel free to contact us with any further comments or issues.
Aspyr Tech Support