Since 1:40PM (GMT+1), websites with a .de domain are not accessible. The name resolution will currently only work if your DNS server has a cached copy of the corresponding entries. Until now, there is no information as to when the problem will be resolved.
In total, all six DNS servers operated by Denic reply with wrong information. If you want to resolve a .de address with them, you will get a reply that there is no such entry.
Within the last minutes, numerours tweets about the problem have flodded the microblogging service Twitter. Servers of various providers have crashed because of the massive increase of requests.
Update: It seems that DENIC fixed the problem. Where the fault was? Stay tuned.
Denic: Probleme mit den .de-Rootservern? – Viele .DE Domains nicht erreichbar, DENIC arbeitet daran. http://j.mp/cvU5b8