Could possibly be a bad tailcap switch but that is uncommon--Sanwu does test them all before shipping.Thanks I have tried all these things. Still no success. I will probably have to wait and see what sanwu says.
Here is a video from Sanwu just in case you need to see how it works.
Are the batteries in correctly--someone mentioned that the Spiker is case negative so positive end goes in first--negative to tailcap---See: http://laserpointerforums.com/f65/sanwu-spiker-case-positive-97361.html