Closing any internet window cause IE 7 to shutdown and relaunch

Since installing NIS 2011, when I close any open internet window, IE 7 shutdowns and relaunches itself. For example, if looking at a product I click on the zoom button to enlarge the picture another window opens up. That's ok. It is when I go to close that window I get a message that the internet is not responding and all open internet windows are shutdown. Next, IE7 then relaunches itself to my home page. How do I stop this?

Thank you in advance.

Paul