This must be something with your game, cause the game is working as it should when it comes to that.
If I were you, I'd make sure that I'd try different rendering modes for the game first. Go into the options menu and change between Direct3D9 and OpenGL, maybe 1 works better for you.
Restart the game and see what happens.
If you still have issues, did you update the DirectX that the game installer asked you for? If you did this, you'd probably want to obtain a new copy of the game and try to install it again, who knows, maybe something was missing in that installer that you need.
And if you did that as well, it might be that you'd want to update your graphic card drivers, though it seems unlikely to me since the game worked for you before, so I'd either go with some sort of ingame setting you need to diddle with or that the installer you installed with were broken.