I'm using Domain Mapping 0.5.4 on WordPress 3.1.4. I have remote login enabled and the set up is subdirectory.
Basically the problem we have is that the user is unable to logout.
This is the error I am experiencing. When the user login to a non-domain mapped URL (e.g. http://site1.mysites.com/wp-admin) and the user visit the domain mapped URL (e.g. http://site1.com) and then go back to the non-domain mapped URL and logout from there, the session is still alive on the domain mapped URL.