For those of you who tried to register today and encountered problems, they have been fixed. To enable your account, just go to this url:

http://www.mangaupdates.com/signup.html?act=confirm&hash=your_hash

And replace "your_hash" with your authentication hash. It will look something like this:

3d927e37c550436e2952035d62687b3e

Sorry for the trouble.