If when trying to open a new session, this opens a new window and closes the old one, then please check the setting below.
Open up Internet Explorer with the system closed.
Click on the cog wheel at the top right.
Select Internet Options.
Halfway down the page click on tabs.
When a pop up is encountered - Always open in a new window
Open links from other programmes in - A new window 
Click ok
Then apply
Then ok
Shut down internet explorer and the system and then log in and try and open new session.