Bind does not resolve host names an returns error.

Hello


We use a Debian Box with BIND 9.2.4
Bind is hosting nearly 800 Domain.
But sometimes, our Dialup User cant resolv Hostnames.
Bind responses with and Servfail.
When i restart the Server the problem is solved, but why
does it stop resolving some domain?

Has anyone had this problem before?
What can be the problem?

Options are
options {
directory "/var/named";
listen-on port 53 { xxxxxxxxxxxxxx };
check-names master warn;
pid-file "/var/run/bind/run/named.pid";
datasize default;
stacksize default;
coresize default;
files unlimited;
recursion yes;
multiple-cnames no;
notify yes;
//forward first;
transfers-in 10000;
transfer-format many-answers;
max-transfer-time-in 5;
};



Dominik Sennfelder