It's a bug in Windows, but unfortunately it has happened to a good no. of folks when doing a large no. of updates. You can try restarting the updates after a reboot, that sometimes gets around the problem. However that doesn't always work, so you could then look at the list of updates and mark that KB2547666 one as hidden. After that you should be able to restart and get the rest of the updates installed.
If all else fails, there are commands you can issue from the command prompt to clear out the folders used by Windows Update. If you run into that, you can pursue this further, but try the above first.
Just took a refurbished laptop out of the box and ran Windows Update. It downloaded 188 updates, and then began to install them. On update #101 (KB2547666), it stalled and has been running there for several hours. The laptop appears to halt the installation when I click "Stop installation," but when I restart Windows Update, it displays "Installing update 101 of 188...Update for Windows 7 (KB2547666)." Any suggestion(s)?