I have had problematic Exchange 2010 and 2007 rollup installations due to security permission issues:
-The update rollup failing in the middle (can be very painful to cleanup)
-The rollup appears to install successfully, but Exchange is not working and all the services are disabled
These issues can be prevented by running the update rollup installation ‘as administrator’. That said, when you right click on the update rollup package “run as administrator” is not an option!
Here is how to do it:
1) Copy the update to a folder like “C:\Update”
2) Click start, right click the ‘command prompt’ and click “run as administrator”. Now anything we execute from the command prompt will be ran as administrator.
3) browse using the command prompt to where you copied the update rollup: “cd\update”
4) hit the tab key or type the name of the update executable and hit enter, the update rollup installation will begin.
Note: If you are running a DAG, here is how to Install Windows Updates on DAG Members.
You may also find the following link helpful in the future if you find that your Exchange 2010 rollups take forever sitting at “Setup Wizard is generating native images for .NET assemblies”