When you've reinstalled the game, did you also uninstall first, by deleting your FeralHeart folder?
I would suggest that you uninstall FH from your computer (as I explained above), then, just to be sure everything is in your computer the way it should be, reinstall it once more.
Then, we're going to change your rendering mode:
1.) Go to your FeralHeart folder, scroll down, and click the folder that says "Ogre.cfg"
2.) Open it with Notepad
3.) There will be a bunch of little codes in the Ogre.cfg file, but I just want you to focus on the very first line, which should say Render System=OpenGL Rendering Subsystem
4.) Change that very first line to Render System=Direct3D9 Rendering Subsystem
5.) Save, then restart FH.
See if this won't fix it for ya. c: As Shallow mentioned, any extra particle files would also cause you to crash, but only if you've exported any maps, recently. I hope we can get this working for ya, Elli~
