I use Vista 64-Bit Ultimate.

Current issue, I'll move my mouse to my second monitor where my 2nd character is. Keyboard commands start going to him, however without moving the mouse back to the first screen/char or alt tabbing focus will randomly get switched back to the main thus causing keyboard commands to go to him.

Note: I am not running as an administrator as my mouse doesn't function properly in game if I do. Trying to test it now to see if that actually solves the focus switching issue however.