Error: already exists previous definition

[Active Venture - Tom]

Hi

We have getting a lot of errors like the following from our BIND 9 
servers (9.5.1.1):

20-Jul-2012 15:26:40.181 config: error: 
/var/named/etc/namedb/conf/zone_0.conf:1529: zone 'xxxxx.net': 
already exists previous definition: /var/named/etc/namedb/conf/zone_0.conf:1529
20-Jul-2012 15:26:46.270 general: error: reloading configuration 
failed: failure

This has never ever happened before and the problem only started a 
few days day, and we did not make any changes to our BIND servers. In 
fact, we have using the same set up and configuration for over 3 
years without any problem until now.

The puzzling aspect is, there is NO duplicated config or zone entries 
at all for the domains listed in such error. In this instance, this 
is the only line found in zone_0.conf:

zone "xxxxx.net" {type master; file 
"/var/named/etc/namedb/zones/0/xxxxx.net"; notify no; };

I will appreciate greatly if someone could offer any advise or idea 
as to what's exactly causing such errors? Thanks vert much.

Regards,

Tom