Sessions userdata doesn't work when I switch IP address to my domain, CI 1.7.3

[eluser]Unknown[/eluser]
Hey guys,

For some reason the $this->session->userdata($data); doesn't work when I switch IP addresses to my server.

My users can't log in, because there's a session stored in cookies?

I am not sure what the problem is, but when I clear cookies, it starts working again... I don't want to send e-mail to 30,000 people telling them to clear their cookies, what is wrong with this? I thought cookies are stored based on domain names?

[eluser]tomcode[/eluser]
Do You have the IP match turned off in application/config.php ?

Code:

$config['sess_match_ip']        = FALSE;