This Is not a known issue in the game.
Has this always happened since you've had the game? Or it was okay up to some point?
Can you start the game right up again and play? Or you need to wait or reboot?
Please attach here the game log:
C:/users/<UserName>/AppData/LocalLow/RomeroGames/EmpireOfSin/player.log
To see the AppData folder you'll need to enable View Hidden Items in File Explorer.
And DXDIAG is a program you run from the Windows search box on the task bar. After running it will open a window and start collecting info with a progress bar in the lower-left corner. When it completes click the 'save all information' button and save it to a file then attach that file here.
Please report the temperatures of your CPU and video (GPU)
1/ before starting the game up and
2/ in the main game menu
3/ after say 10 minutes' play, if possible
If your PC's vendor has given you no way of reading temperatures, install
SPEEDFAN
http://www.almico.com/sfdownload.php