Hey-o!
It could also be the shortcut to the extension of the game. Have you tried going into the files and hitting the main extension from there? That has been an issue for me before - just the shortcut stopped working. If that is the case, you could just throw a new shortcut onto your main desktop!
So the game immediately crashes the moment you're starting it up, eh?
That does sound like it could be something wrong with the file.. maybe something is left behind that isn't letting the game run properly? Are you sure you've removed everything and starting fresh?
Another thing you can try is changing the Rendering Subsystems and seeing if that does anything. It'll be located in the main FH folder with a notepad 'ogre.cfg.' Try switching the top line with the other rendering system.
Hopefully something works out for you!