Norton's Internet Security suite includes one of the more common pop-up blockers. To find out if your macine is running Norton, look for the Norton icon in the system tray (the area to the right of the clock in the lower right corner of your screen).

If you do have Norton installed and active, you will need to temporarily disable it.

 To disable Norton's Pop-up Blocker:

1. Right click on the Norton icon which should be displayed in your system tray
2. Choose "Disable" from the drop-down menu
3. Turn Norton back on when you are done with your Vista session by repeating step 1 and choosing "enable" from the drop down menu.