Please identify which security update you are talking about. Is there a KB number you can cite?
Did this update come through Windows Update? Have you attempted to download and install it manually? If so, please provide the link to the download.
You can also try these steps:
A. Click on Start and click on Control panel.
B. Go to Program and Features.
C. Scroll down to Microsoft.Net Framework 4 Client Profile, right click it.
D. It will give you a choice of Uninstall/Change, click it.
E. Then, it will give a choice to Repair it, pick Repair it. It will take about 4-10 minutes to repair (with my PC) your experience may vary.
F. When completed, go to your update center, and update it again
Cheers, however I've not had much luck with that solution.
Went through A-D yet "Repair Did Not Suceed" was the uplifting reply I got. Microsoft .Net Framework 4 was no longer in Programs & Features, went back to Windows Updates where it told me of an important update "Microsoft .NET Framework 4 Client Profile for Windows 7 x64-based Systems (KB982670)" which installed. checked for updates and the two initial Microsoft .Net Framework 4's are back and failing to install. The merrygoround of failure goes on.