user refuses to logout

Hello,

We just launched a new website with a couple of 3rd party software, so we used .net's provider.

But before we could get the membership running and synchronized with all sub domains we tried a lot of tricks here and there.

PROBLEM: Now on one of our browsers a signed in user refuses to logout, its funny, 'cause we dont know which domain or when he was signed in.

We have tried redirecting it to onpage_load event

using

 

 FormsAuthentication.SignOut();
        Roles.DeleteCookie();
        Session.Clear();

but we still cant log him out, what do we do ?

Thanks
...