I am currently using a subdomain wpms install on a dedicated ip. I have installed Domain Map and users point A records to me, where I map external TLD to our subsite.maindomain.tld
Now here are the problems. We have had this working fine with all domains when set to have Admin and Login use the Mapped Domain. No problems with Ultimate FB, etc. However we noticed the Edit Image/Media options no longer worked. We couldnt quickly tweak existing things in the visual editor.
So we pulled the domain mapping to have it log in to the Original Domain (subdomain.oursite.com)
Now whats happening is users randomly get bugs when attempting to login or logout. The admin features work, but the if someone uses the logout link in dashbar, it never logs them out of their site. They have to go back to mainsite to logout. They can login to site, and navigate around find, same issues with logout
I have tried allowing people to log in using the mapped/original domain, but of course the admin dashboard errors out.
There have also been reports of people editing things from originaldomain.mainsite.com, previewing on a mapped domain which gives them mappedodmain.com?preview=blahblah
..and when they do that, they get insufficient permissions errors.
Now what is even more interesting is it seems @Aaron is using Ron's MU Domain mapping plugin