Caching question BIND 9 help me please

[Vo]

Here's my situation.  I'm using BIND 9, Redhat 9 latest version.  I have 
2 servers in house, a primary and secondary, and I'm using my ISP as a 
tertiary.  

Last week my primary suffered a hard drive failure.  I thought "no big 
deal, the secondary and tertiaries will take care of servicing DNS 
requests". The primary was down for about 28 hours while I got a new 
hard drive in place.

During this timeframe the secondary was reporting constantly that it 
couldn't update since it couldn't reach the primary. I expected that.

At about 24 hours elapsed time, we started disappearing off the 
internet.  Using my secondary to query some names from my domain, I got 
"not founds."  I did that with our ISP tertiary DNS server as well, and 
was spewed back the root servers list.  Not good. (I quickly got the 
primary back online and everything straightened out straight away).

My first thought it that I have the caching info set incorrectly for my 
domain.  Here's an obfuscated version of my DNS record for my domain:

$TTL    86400
@       IN      SOA     dns1.me.com. postmaster.me.com. (
                2003042101      ; serial
                1H      ; refresh (1 hour)
                30M     ; retry (30 minutes)
                7D      ; expire (7 days)
                1H      ) ; minimum (1 hour)

                NS      dns1.me.com.
                NS      dns2.me.com.
                NS      ns1.myisp.net.
                NS      ns2.myisp.net.
                NS      ns3.myisp.net.

 { address records and cname records here  }


Is my $TTL setting what killed me?  Everything else seems to be set for 
a 7 day expire and I'm probably missing something insanely simple.  
What's a good setting for a stable network with no significant changes 
being done for these?

Thanks in advance, y'all.

Vo