[CentOS] named 'wedging' on CentOS 4.7

For some unfathomable reason, named 'wedges' -- becomes unresponsive and
needs to be killed (with -9!) and restarted.

I am using an intermittent (it is not a dedicated phone line -- I also
use it for voice calls), dialup connection to the internet and I am
using forwarding (from /etc/named.conf):

options {
        directory "/var/named";
        dump-file "/var/named/data/cache_dump.db";
        statistics-file "/var/named/data/named_stats.txt";
        /*
         * If there is a firewall between you and nameservers you want
         * to talk to, you might need to uncomment the query-source
         * directive below.  Previous versions of BIND always asked
         * questions using port 53, but BIND 8.1 uses an unprivileged
         * port by default.
         */
        // query-source address * port 53;

        listen-on {127.0.0.1; 192.168.250.1;};
        forward first;
        forwarders {
                128.119.100.21;
                128.119.100.84;
                128.103.38.67;
                64.74.153.161;
                208.76.56.56;
                208.76.62.100;
                75.102.60.66;
                78.129.207.168;
        };
        notify no;
        heartbeat-interval 0;
        interface-interval 0;
        dialup passive;
};

I have a local LAN (right now, just my desktop and my Laptop run most
of the time, sometimes other machines are connected and fired up) and
use the local named for local DNS requests (I run Apache on this
machine with a pile of virtual hosts for web-site testing).

Every so often, named just goes south.  It can't be restarted (eg
'/sbin/service named restart' hangs) -- I have to use killall -9:
'killall -9 named' and then start it up.

I am using CentOS 4.7 and the stock bind:

sauron.deepsoft.com% rpm -qa | grep ^bind
bind-libs-9.2.4-30.el4_7.2
bind-chroot-9.2.4-30.el4_7.2
bind-utils-9.2.4-30.el4_7.2
bind-9.2.4-30.el4_7.2

What should I be checking for?

-- 
Robert Heller             -- 978-544-6933
Deepwoods Software        -- Download the Model Railroad System
http://www.deepsoft.com/  -- Binaries for Linux and MS-Windows
heller at deepsoft.com       -- http://www.deepsoft.com/ModelRailroadSystem/