Most vexing.
On the "Features" page of the Launcher, there is a field called "Custom flags". Could you type the following on that field:
-res 1920x1200
then try and see what happens?
Also, select debug log, run and post the debug log.... OpenGL init might have some valuable info about what resolution the game tries to run at and why.
You could also try and see if any of the other changes in resolution options affect things at all.
Oh and also, the interface is limited to 1024x768 resolution due to technical reasons, but the in-game 3D rendering should be doable on just about any resolution. Is it possible that this has simply confused you, or does the 3D also render at low resolution?
omg ninja'd again... but if the resolution command line trick doesn't work, check the other stuff.
EDIT:
Initializing OpenGL graphics device at 1920x1200 with 32-bit color...
Initializing WGL...
Requested WGL Video values = R: 8, G: 8, B: 8, depth: 32, double-buffer: 1
Actual WGL Video values = R: 8, G: 8, B: 8, depth: 32, double-buffer: 1
OpenGL Vendor : ATI Technologies Inc.
OpenGL Renderer : ATI Radeon HD 5800 Series
OpenGL Version : 4.1.10660 Compatibility Profile Context
Your video card works perfectly!
In other words, it seems like it's just the interface that is on low resolution. While there's nothing we can at this point do about that, your game should actually run at native resolution of your display while you're in-game.
