Bind dies and permissions changed

[evilphantom]

Last night the Bind service died. Upon inspection I noticed the following:

Jun 2 22:38:17 db1 named[2452]: message.c:808: REQUIRE(*rdataset == ((void *)0)) failed
Jun 2 22:38:17 db1 named[2452]: exiting (due to assertion failure)

and the following occured when trying to restart the Bind service:

Jun 3 09:37:21 db1 named[25717]: starting BIND 9.2.1
Jun 3 09:37:21 db1 named[25717]: using 2 CPUs
Jun 3 09:37:21 db1 named[25719]: loading configuration from '/etc/bind/named.conf'
Jun 3 09:37:21 db1 named[25719]: /etc/bind/named.conf:39: open: /etc/rndc.key: permission denied
Jun 3 09:37:21 db1 named[25719]: loading configuration: permission denied
Jun 3 09:37:21 db1 named[25719]: exiting (due to fatal error)

I changed the permissions from to 644 on rndc.key in /etc/bind/rndc.key and restarted. and everything was fine. I did this misreading this line: open: /etc/rndc.key: permission denied
thinking it had said open: /etc/bind/rndc.key: permission denied

The current permissions on: /etc/rndc.key are 640

neither file is a sybolic link either

But I am confused now.
A) why did it stop?
B) why did changing the permissions on a file that wasn't associated with the daemon work?

Thanks

Dez