DNS lost SITE time to time

Hi fellows
have a pretty new site (2 weeks only)
I have faced a interesting issue
my site time to time -1 time per week totally lost from DNS

but on other DNS providers (GOOGLE, OpenDNS etc ) it works good

I see one of your nameservers looks broken:


ns5.be-dns.net returns REFUSED for gixo.co.uk/A
ns4.be-dns.net is authoritative for gixo.co.uk

i see where is the problem