How To Fix Strange Problems with Internet Explorer December Security Update

Users reported experiencing odd browser behavior after installing the most recent security update which has been identified as being caused by a registry key.

Problem:
Some reported opening a browser window that promptly hangs IE, others have reported opening links that render blank. There are also reports of multiple windows opening when initiating a browser session.

When:
This can happen if a user has ever attempted to run IE7 Beta1 in an unsupported side-by-side configuration with a version of IE6 or after a failed IE7 installation.

Solution:

To address this issue on a machine running IE 6 SP1 with our most recent security update, locate and delete this entire key from the registry of the affected machine: HKEY_CLASSES_ROOT\CLSID\{c90250f3-4d7d-4991-9b69-a5c5bc1c2ae6}. If you are running IE7 Beta1 in a side-by-side scenario with another version of IE, this is not a supported scenario. Please uninstall and reinstall IE7 Beta1 in the recommended manner.

Source: IEBlog