The .DE .AT .RU .SE .NL & .ES Registry requires all domains must indicate at least 2 and no more then 5 nameservers, in order to ensure a registration or the accessibility. These nameservers must be in numerus different "Class-C" Networks. The registry will check whether at least one of the first three segments of the IP address is different from the corresponding segment of the IP address of the other nameservers.
PLUS: All the authoritative name servers for the new zone must be indicated. Also, all the matching SOA records (SOA = Start Of Authority) must be uniform and must fallwithin the following guidance values (indicated in seconds):
refresh : 10000 - 86400
retry: 1800 -28800
expire: 604800 - 3600000
ttl: 180 - 345600
Additionally the nameservers must be configured in accordance to The registry requirements, otherwise NO DELEGATION will take place and your domain will NOT RESOLVE!
Please refer to: http://www.denic.de/en/background/nast.html
NOTE: These restrictions are put in place and enforced by the country code domain name registry, not iDotz.Net. We are UNABLE to correct your nameserver issues.