If you are still unable to install updates after reseting the Windows Update components, you may try to boot the computer in clean boot state and try to install updates.
To perform a clean boot on a computer that is running Windows Vista:
1. Click Start, type msconfig in the Start Search box, and then press ENTER.
If you are prompted for an administrator password or for a confirmation, type the password, or click Continue.
2. On the General tab, click Selective Startup.
3. Under Selective Startup, click to clear the Load Startup Items check box.
4. Click the Services tab, click to select the Hide All Microsoft Services check box, and then click Disable All.
5. Click OK.
6. When you are prompted, click Restart.
7. After the computer starts, run Windows Updates and install the available updates.
Note: Make a note of all the updates those were installed. You can do this by reviewing the update history from Windows Updates website, by opening it from the control panel.
If your issue is resolved after performing Clean Boot and then installing the updates, access the link below and see the section on how return your computer to a Normal startup mode by following the steps under “Reset the computer to start as usual”. http://support.microsoft.com/kb/929135