Hello,
Klaus-Jürgen kindly forwarded me your e-mail, so I'll reply inline. Note: Please Cc me on replies, as I do not read this list.
I think I know what's happening. I haven't answered a number of the
anti-spam questions correctly, and the time for which I'm blocked is
*really* long.
What's the blocking message? I haven't configured our Captcha so that it locks users, at least not on purpose, so I'd like to have a look whether that is really the culprit or some other plugin.
The problem is that we have heavy spam problems, being one of the largest free software projects. Rather than switching to manual account approval, we decided to leave the registration open, but that means we have to take some provisions. Just as with e-mail spam filtering, they are never 100% perfect, neither in terms of false positives nor false negatives. 
As for the questions I'm getting wrong, here are some (paraphrasing):
What's the 3 letter acronym for this organization? I typed TDF but that
wasn't correct. Perhaps it's expecting lower case?
TDF in upper case is correct.
What's the street abbreviation without number? I typed Kurfürstendamm.
No idea what the abbreviation would be since I'm not German.
Sorry for that glitch - it indeed contained the old address. The new one has a special character (Umlaut) in it, so I completely removed that question now.
What's the phone number for TDF? I've tried "609856720" and "30
609856720". My next try will be "+49 30 609856720"
That sounds about right. 
Anyway, long story short, I'd say some of these questions either have
unexpected answers or non-obvious ones for English speakers like me.
Furthermore, being locked out for a day or more seems excessive :-).
Sorry for the bad experience you made, that's definitely not what we intend. I have fixed one of the questions, and if you let me know the exact error message about locking, I am happy to have a look.
You can also let me know your desired username, then I create the user manually for you.
Florian
