Pictures in attachment are showing problem in IE. So, if compatibility mode is turned on, user keeps getting logged out after some time, but if it is turned off, user cannot login at all.
Session only settings. I made screenshots from user computer. This thing happens on several computers. As there is user limit, like 3 concurrent users can be online or something like that. Or 5 minutes you an be inside and that is it. Cannot use cookies because they keep getting users very unhappy .. :D at least the way it is done in EE.