Windows update will not work

I am trying to update some security patches via windows update, and the operation keeps failing! I know its not the BLASTER virus, because that patch was previously installed, and to be sure, I manually checked, and ran the Symantec tool, just to be 100% sure. Usually if the Microsoft site is overloaded, I will get a “server busy” message, or the checking for updates will be very slow, but in this case the operation starts and I get a message that it failed to install the updates.