My b2evolution Version: 2.x

I just installed b2evolution and almost everything works fine. I "just" have problems being logged out automatically although I accept cookies. This also happens when I clean the cache and temporary Internet files. It happens both with Internet Explorer and Firefox (I haven't tested Opera yet).

This problems doesn't occur when I am just working in the backoffice but as soon as I switch between different open tabs/windows and return then to b2evolution backoffice I have to login again to continue working.

I have already read the FAQ article "I can log in but b2evolution asks me for my password again and again / my cookies don't hold" (in the Docs Section) but the suggestions there haven't solved my problem.

I also tried to serach the forum for a solution but wether there aren't any answer or I have search with wrong terms. Anyway I need some help to solve my problem since I have no idea what's wrong.

Session timeout is set to 604800 secs so this shouldn't be the problem. baseurl is set to the right address. I double checked.

Does anybody know what else could be the reason for my problem and how to change this behaviour? It's very annoying when you have to login in again and again after switching to another tab/window!