Did you ever play with trying to enable Stereo3D due to changes in the system.cfg or autoexec.cgf? In that case it might be that after Crytek reenabled 3Dstereo support you game started in split screen 3D mode. If thats the case just disable the 3D stuff.
Hey man I had this too, soo anoyinging it's to do with the resolution try alt tabbing then hitting al and enter a hundred times until it fixes itself. Seriously this what I have to do everytime I launch Crysis 2 from now on. Like wtf seriously ?