sometimes it resolves sometimes not

[Woger]

Hi there,

We have several servers running as webserver and also running named on
FreeBSD. All servers are running well but 1 server has a problem that
some of the domains on the server aren't resolvable for a few hours. I
can resolve the domains from all the servers in the ip range, but my
many ISP's don't resolve. After a few hours everything is working
again. I don't know where to search.

Roger