How odd. Microsoft is the target of an attack today, so this could be a partial factor.
Does this link work?
http://v4.windowsupdate.microsoft.com/en/default.asp
Suggestion 1:
Make sure your antivirus definition file is current.
Make sure there are no third party ad blocking programs or accelerators running.
Run ad-aware to make sure you are clean from hijacks, adware, and spyware.
Reboot the computer and try again.
Suggestion 2:
Check your IE security settings:
1. In IE click TOOLS -> INTERNET OPTIONS -> SECURITY -> CUSTOM LEVEL
2. Make sure that "File Download" is enabled.
3. Make sure that "Run Active X controls and plug-ins" is enabled.
4. Make sure that "Active Scripting" is enabled.
5. Set your Java Permissions to "Medium safety."
6. Make sure that "Launching applications and files in an IFRAME" is enabled.
Suggestion 3:
If it still isn't resolved, you can try the following:
1. Open IE, Click TOOLS -> Internet Options -> Connections -> LAN SETTINGS
2. Delete anything in the Automatic Configure text box and clear the "Use automatic configuration script" check box.
Suggestion 4:
The hosts file or windows update shortcut might be corrupt. Let's try the others above first.
Suggestion 5:
Throw it out the window and see how many times it'll bounce.

(please skip this step)
Let us know if any of the above fixes the problem.
Mike