WordPress MU

I have setup a Wordpress MU, and have made two blogs.

blog1.domain.com
blog2.domain.com

blog1 is the primary domain for the install.

I have setup my CNAME to point to blog2 to the IP address of the server and the blog shows the standard "hello world" for the correct blog.

I can login to Blog1 as administrator and everything seems fine, until I try to login to the dashboard of Blog2.

At which point, when i try to login the system with an INCORRECT password, the system says "Invalid username / password" - but when I login with a valid username / password, it just takes me back to the blog2 login screen, but doesn't take me to the dashboard.

Any help would be great.

Thanks.

oh and I have the domain mapping plugin by donncha installed

Have you actually used the domain mapping plugin yet?

As far as I can tell? I installed the domain mapping plugin, but I didn't actually set anything up in it? when i try to add the subdomain in the 'domain mapping' it says the subdomain already exists

Yeah, becasue you don't map an existing subdomain to itself. the plugin is for when you want a full domain name to show up *instead* of the subdomain.

you know, how when you have a blog at wordpress.com? They have a paid add-on for domain mapping so the blog has tis own domain name.

you are setting up the exact same thing on your site, minus the payment part.

I think it got it now, but I'm getting a "Unknown login key" problem now..

any idea?