Cart don' work anymore on subdomain

[eluser]Unknown[/eluser]
I can't add item to cart since I moved on subdomain
I think this is a cookie/session problem
Before on www.domain.com work fine,
when I moved all on shop.domain.com don't work anymore!
I tried all combination in config file
$config['cookie_domain'] = ".domain.com";
and
$config['cookie_domain'] = "shop.domain.com";
but with firebug I see domain name= ".shop.domain.com"
How to remove "." unnecessary?

Anyone can help me?