Key no longer valid

So I purchased a registered copy of Torsion last year, which for some reason decided today that it is no longer registered and is asking for the registration key again. Problem is, it's saying my registration key is not valid. Any reason why this might have suddenly happened, and why the key is no longer valid?

[b]Moderator Note - I've stickied this thread so it is always at the top. Please post here or e-mail support@garagegames.com if you encounter this problem. You must have a previously valid Torsion key in order to get a new key to fix the issue.