The same thing happened to rudgar. I've reset your user status to 'valid', so your privileges should now be restored. Undertow for some reason doesn't like German e-mail addresses.
For rudgar, our site owner (detritus) suggested that he change his e-mail to a different service (such as gmail).
The issue was on our end. Thanks fleet for keeping an eye on these and manually approving. Our e-mail server was getting a pounding from hackers and was going down for several hours at a time. I'm taking some steps to take the pressure off it and get it stable. Sorry for the inconvenience!