This is the scenario...

I'm logged in to the Admin area. No issues.

I open the mainsite in another window and navigate to the News Headlines page where I've included summary.php.

Back in Admin, when I try to perform any action, I'm logged out and taken back to the Login screen.

I login again and close the other window. I'm able to perform all actions in the Admin. I stay logged in when I switch over to the Blogs.

The moment I open the News page again, I'm logged out.

Thought I'll let you folks know...

This could be related to this topic http://forums.b2evolution.net//viewtopic.php?t=12785