We are currently having issues with our DNS servers which are hosted at OVH (in a globally distributed manner). OVH just announced to have severe network issues affecting the entire OVH network.
At least ns.ks-dc.info (184.108.40.206) seems to be affected at the moment.
UPDATE 18:40 CEST (UTC+2):
The issues have been resolved. We apologize for any inconvenience these issues may have caused.