zone file got overwritten

[Alan Chung]

Hi,

I have been experienced some strange problem with my bind 8.2.3-REL version 
on redhat 6.2.
I compiled from source with standard procedures.  But every once a while, 
one of my zone file will be always overwritten by some kind of dumping 
program of bind.  The following is how the file looks like after that,

;BIND DUMP V8
$ORIGIN 168.192.in-addr.arpa.
1      86400   IN      NS      ns.user.com      ;Cl=5
         86400   IN      NS      ns.hot.com.        ;Cl=5
         86400   IN      SOA    ns.user.com. postmaster.i-escrow.co.jp. (
                 2001050802 1000 3600 604800 86400 )    ;Cl=5
$ORIGIN 1.168.192.in-addr.arpa.
136     1200    IN      PTR     host1.user.com.   ;Cl=5
102     86400   IN      PTR     www.user.com.   ;Cl=5

My original zone file is gone and even I changed the file without writable 
permission, it still got wiped out.

Does anyone know what this is?

Alan