Have you downloaded any mods (items, markings, etc) for the game recently? Maybe a misplaced file is messing everything up
I would also try changing rendering systems. To do this (without getting in-game), go to your main FH folder and open up a file called "ogre.cfg" At the top it will say "Render System=Direct3D9 Rendering Subsystem" (or "OpenGL" in place of "Direct3D9" if your game is currently on OpenGL). Now, just change it to whatever rendering system you're currently not using. Now, at the top it should say either (feel free to copy and paste this):
Render System=Direct3D9 Rendering Subsystem
or
Render System=OpenGL Rendering Subsystem
Now just save and see if the game works c: