The problem that certain web site doesn't seem to function is that Pop-up blocker embedded with IE7. For security reason, your computer will block you out from log into that site without your permission.
To change the settings of the Pop-up Blocker within IE7:
There's also Notification and Filter Level, you can configure Internet Explorer to play a sound and show the Information bar when a pop-up is blocked. So it will be less confused next time if you felt that IE7 silently shut you off from certain web site.
If you like to block out certain web site out from your computer, check here