"Error loading configuration file"

[Mudbill]

I'm guessing you got it for Steam then. You can first try verifying the integrity of the game, then also check to make sure you have no custom start flags added (in properties > set launch options). Other than that, it might also be an issue with the OS, because the game had a lot of struggles on Mavericks that might still be present in Yosemite. Some said the Penumbra games were working on it though, so it might be possible to fix this time around.