If you are running AtGuard, disable it when you want to update windows.  I had a similar problem and Microsoft sent me a detailed letter on how to correct it.  (I know, they actually responded)   Their response is as follows:

1. click start, then run
2. type msconfig
3. click OK to launch the utility
4. click on the startup tab
6. next uncheck all of the applications but systemtray and explorer (if explorer isn't there that is OK) then click OK
7. reboot (Do this AFTER you have finished the steps below - To start up normally go back to msconfig and on the general tab select normal startup)

Troubleshooting steps

1.  Clear Internet Explorer Cache and History
a. click Tools on the top toolbar of IE
b. select Internet Options and then click the General tab
c. in the Temporary Internet files section, click delete files
d. Mark the Delete all Offline Content check box and then click OK
e. In the History section click clear history button
f. click OK

2. Remove items from the WindowsUpdate folder:
a. Click Start>programs>Windows Explorer
b. In your C: drive, open the program files folder then open the WindowsUpdate folder
c. In the right pane highlight  wuhistv3.log and click Edit > Invert selection
d. press the delete key  click yes to confirm

3. From the start menu select run - type:    regsvr32 wuv3is.dll /u
a. Click OK
b. Click Start/find/files or folders
c. type  wuv3is.dll in the named box.  Make sure you are looking in the C: drive
d. once you find it, right click and delete

4. remove the site control (if you don't find it skip this step)
a. right mouse click on the start button and select explore with the left mouse button
b. double click on the downloaded program files folder (in the C: drive)
c. right click on the file   cv3 class   and remove this file
d. empty the recycle bin

5. reboot the system and you should be able to access the Windows Update site.

This is word for word what Microsoft sent me for instructions.......and they worked
Good Luck