I had a similar problem with the Power/Light button. I got my watch replaced under warranty, but if yours is out of warranty, then you could try as a last ditch attempt giving the watch a bath in lukewarm water with some mild detergent (like soap). Just soak the watch for half an hour, shaking it vigorously under water several times. Remember NOT to press any buttons when the watch is submerged. If this does not help, then I am affraid that replacement is the only option.
