I'm wondering if all versions of Windows 7 on a home group network must match (e.g. all RC or all RTM)? I was unable to add a new Windows 7 RTM to an existing Windows 7 RC HomeGroup. It simply spins for a while after entering the password then eventually allows you to hit next again.
The troubleshooters (on both boxes) didn't fix it. I'd like to delay updating my media center to RTM until later.
I'm going to try taking down the HomeGroup and making a new one from scratch.