axolotls; you have a most unusual problem, one that I have never encountered in the 50 or so Mag Lights that I have purchased. I would send it back to Mag and get it replaced.
My experience is that the C/D MagLights are extremely dependable. You can bang them around, drop them, leave them alone for a couple of years, and they will still work. The switch automatically rotates the contacts, so that the contacts keep clean. I can't think of a more rugged light.
The other sizes are a different story. The Solitaire is abhorrent. It will frequently not light up if it hasn't been used in a few weeks. If you work the switch a few times, it usually then works normally. Also, the switch tends to turn on by itself in your pocket, so that the thing is really dead next time you try it. Photons and ASP lights have rendered this light obsolete.
The AA and AAA lights are also plagued with switch problems, but not to such a large degree. They will usually work if you turn them on and off a time or two. This problem tends to crop up only when the light has been stored for several months. The real problem with these lights is the small amount of light you get for the size and weight. Sure Fires are much better choices.
Hope this helps, Walt