If you have installed any ad blocking software like Pop-Up Stopper, AdsGone PopUp Killer, Stopzilla, EndPopups, etc. that disables pop-up windows, you will need to disable it. Some applications may allow you to temporarily disable them while other programs require that you remove them. Some internet security software like ZoneAlarm Pro and Norton Internet Security also include ad blocking software and those must be configured to allow pop-up windows. The same software that blocks pop-up ads also interferes with Blackboard's Collaboration Tools (virtual classroom and lightweight chat).