The Y-axis sensitivity is based on FPS while the X-axis isn't. Because indoor FPS is so much higher I find that when I'm indoors moving the mouse along the Y-axis at all shoots me to the ceiling or the floor.
Go into your catalyst manager and change AA from adaptive to multi sample to get rid if the transparent /flickering textures.
I already did and still had issues, but the game looks just fine with FXAA alone.
Can anyone else who is having issues test this? I'm curious if this fix is specific to my system. All you have to do is alt tab out, then back in once you load a game.