Rebooting stops resolving for a while

[Gary Mayor]

Hi,
When I reboot my server sometimes my domains and mail servers are not 
available for an unknown amount of time but after several hours 
everything returns to normal and everything can be accessed. The strange 
thing is if after a reboot I try to access the domain or mail server 
from my machine at home it doesn't work but if I go somewhere on the net 
and try a ping test from somewhere else in the world it always works. 
Can someone take a look at my main zone file and and a client zone file 
and tell me if anything doesn't look right.

Main Zone File
$ttl 38400
mydomain.com.	IN	SOA	55.55.55.55. mydomain.com. (
			2003111224
			10800
                         3600
                         604800
                         38400 )
mydomain.com.	IN	A	55.55.55.55
mail.mydomain.com. IN	A	55.55.55.55
smtp.mydomain.com. IN	A	55.55.55.55
www.mydomain.com.  IN	A	55.55.55.55
ftp.mydomain.com.  IN	A	55.55.55.55
mydomain.com.	IN	NS	ns1.mydomain.com.
mydomain.com.	IN	NS	ns2.mydomain.com.
mydomain.com.	IN	MX	5 mail.mydomain.com.
mail.mydomain.com. IN	PTR	mydomain.com

Client Zone File
$ttl 38400
clientdomain.com.	IN	SOA	abertron01. gary at abertron.co.uk. (
			2003111245
			10800
                         3600
                         604800
                         38400 )
clientdomain.com.		IN	A	55.55.55.55
mail.clientdomain.com.		IN	A	55.55.55.55
www.clientdomain.com.		IN	A	55.55.55.55
ftp.clientdomain.com.		IN	A	55.55.55.55
clientdomain.com.		IN	NS	ns1.mydomain.com.
clientdomain.com.		IN	NS	ns2.mydomain.com.
clientdomain.com.		IN	MX	5 mail.mydomain.com.

Basically nothing works from from home computer after I reboot the 
server but I seem to be able to access the server from elsewhere after a 
reboot so what on earth is going on here.

I'm totaly confused any ideas.

Thanks

Gary Mayor