Do you have Firefox set to remove cookies when it quits (Preferences > Privacy > Clear Private Data tool)?
Nope
On the other hand, it might not be an issue with your settings at all necessarily. Do you have crappy dialup or some such where your IP address changes randomly? That could do it.
My Internet connection is via LAN T3 (I get IP with DHCP at the start of the comp, and of course it is not public IP)
I have also 5 cookies (as rasz_pl):
phpbb2mysql_data (expires: 2007-09-28 - in a year from now)
phpbb2mysql_sid (expires at the end of the session)
__utmz (expires: 2007-03-24)
phpbb2mysql_t (expires at the end of the session)
__utma (expires: 2038-01-18 !!!)
BTW. Hey next_ghost - the script is great - thanks!