IP Firewall disconnecting me after firewall changes

[Brett Davidson]

I keep firewall rules in a file that I then run via a "sh" command. You
know, like /etc/rc.firewall. :-)
 
Essentially the file does 
ipfw -q -f flush
$cmd 0015 check-state
$cmd set 31 <rule#> <allow tcp from <address/subnet> to me 22 in via
$pif setup keep-state
 
where $cmd = "ipfw -q add"  and $pif = "em0".
 
I understand that this set 31 rule should remain even after the flush
action on the first line.
 
This does not appear to be the case. If I run this script from an ssh
session I get disconnected which is not what I expected. 
 
What am I doing wrong?
 
Cheers,
Brett.