hi volker
i tried to register yesterday and today and used a gmail.com email adress.
unfortunatly i didnt receive the activation response.
today i registred here with an web.de email adress and it worked.
dont you like gmail? 
seriously - have you blocked any tld?
and one proporsal: could you allow in one forum posting whitout registration?
it would be easier for the people that cant register....
greetz
netlord
