Process Priority changing on it's own

I recently installed Sid Meier's Civilization 4 on my Windows 8 64-bit machine. Now I am having the issue where the game sets it's own process priority to below normal. If I try to change the priority to above normal, within a few seconds it sets itself back to below normal. This causes my computer to minimize the whole game every few seconds.
Does anyone know what causes this or if there is anything I can do?