45 degree lines not snapping correctly

I have a problem when trying to make 45 degree lines of a certain length. When i use the command prompt to enter the length for the line, it snaps to 90 degree angles, instead of the 45 degree angle that is indicated when hovering the mouse using polar. When i click to set the end point of the line, it works, but diagonals do not work. Any ideas about what is causing this?