Alright, before anyone says so... I've seen the stickied thread on the top of this, and already tried that. It did not work.
Here's the deal. I'm trying to run Istaria at either 1920x1080 res, or 1600x900 res. I will edit the the file that is stated, and nothing will happen. It will not add the the end of the list. If I do the other method and delete everything but the resolution I wish the game will act as if there are no resolutions are all, and refuse to start in anything but windowed mode. Windowed mode which apparently has a very high resolution I may add.
I would prefer to play this game fullscreen at a high resolution, but at this point I am stuck about how to do this, or why the above methods are not working. Er.... help?