said by stevadson:
Perhaps it has something to do with this (from the KB article):
Known issues with this security update
In certain automated update deployment scenarios (such as from Windows Update or Microsoft Update), this update may not always install. This would also cause other pending updates not to install. For more information about this issue, click the following article number to view the article in the Microsoft Knowledge Base:
2552343 Time-out error occurs when you install a Windows Update package that contains drivers on a computer that is running Windows 7 or Windows Server 2008 R2
This issue can occur with any windows update package that contains drivers on systems that do not have the critical non-sec GDR update 2552343 installed.
We recommend that you install update 2552343 before you deploy this security update.
I thought you might be on to something espcecially when the next poster reported he had KB2807986 checked. I thought maybe I had not installed KB2552343 and therefore WU would not check KB2807986 for installation but I have installed KB2552343 in July 2011 so that's not it.
So now the question is why KB2807986 would be checked for installation on some computers and not others?