So recently installed .NET Framework 4 on my Windows 7 laptop because I needed it for a new app. Afterwards I naturally needed to install a slew of updates from our WSUS server to go along with it. Two of them said they would install, but would pop back up as needing to be installed later on. I looked into it, and the KB numbers aren't important because it could happen with any of them.
What IS important is how to fix this irritating issue. On some of the forums I visited, people had run the installation 30 times or more with the same result! I facepalmed when I read that you need to use the venerable .NET cleanup tool to remove the offending numerical .NET version you are having issues with, and then reinstall from the standalone installer which you can get from Microsoft's downloads page.
I have used the .NET cleanup tool, which you can find at Aaron Stebner's blog here, before to clean up all kinds of .NET shenanigans - weird error messages and the like, so I can't believe I overlooked this great tool when confronted with a .NET issue.
Nuke it from orbit, it's the only way to be sure.