Cross Domain Login doesn't seem to be working properly

Domain Mapping is working properly in my site. Main site is http://www.ogerente.com.br, and subdirectory mapped site is http://www.stakeholdernews.com.br.

The problem is when I login to http://www.ogerente.com.br, and then visit http://www.stakeholdernews.com.br, I'm not logged. If I want to comment on a post, for example, I have to log in again in the mapped domain.

I have the "Cross-domain autologin" set to YES.

Any ideas on how I can solve this?

Thanks!