Usually when the one-time password stops working it's because your token or app is out of sync with the server. There isn't anything you can do about the physical token besides getting a new one (the batteries may be dying and you can't replace them), but the smartphone app can be resyncronized in the settings menu. In the mean time you can always do what dejixal suggested and simply remove the token from your account until you can find a solution.

Also, next time try being a little more specific, it makes it easier to provide help. It's not fun having to guess at the solution to someone's problem because they're being vague. If you work in customer service you should know better!