If you try to login multiple accounts of a particular website with two different logins, you may not be successful. Internet Explorer has implemented an incomprehensible feature that has multiple open browsers sharing the same session. Besides being a large security hole (ability for a person to open a browser window and access sensitive information from a different window) it may break our applications (InQuiry and InCommand) that are expecting separate sessions across separate browser sessions. This is because, IE by default, uses the same "session cookies" among its tabs and windows.
To get around this, there is an IE option switch -nomerge that you can use.
This starts a new browser window in a new, unique session. Note that even after using the -nomerge switch, you still have to open a new IE windows and not just a new tab.
To start Internet Explorer in this mode, type iexplore.exe -nomerge in the Start search box, and hit "Enter".
Alternatively, here is a way to have Internet Explorer start this way via a shortcut each time without having to manually type in the switch. Right-click one of the IE8 icons and select "Properties".
Select the "Shortcut" tab and in the Target box add at the end (shown & highlighted below): -nomerge. Then click "Apply", and then click "OK"