Somehow you are using the wrong link. Maybe your email client damaged it. Or maybe you are not cutting or pasting properly. But you can activate without using that link. Here is an excerpt from the sticky thread at the top of this form describing how to handle activation problems:

If you have the activation code, you can enter it manually together with your user name on: The Activation Form

So click on that link. And enter your name and the activation code from your email.