Grounds are funny. You think they are good and then all of a sudden they are not as good as the were before.

Also check your switch handle. Can you move it perpendicular to the normal way the switch moves? If you can, try to tighten the screw that holds the lever in the switch. You switch may not be making contact with-in itself. Sounds goofy, but I had one do this for me.

It's a bear until you find it. Then it is something really simple and you just shake your head at it.