Why does Xcode still show up as an available update in App Store after being installed?

I have installed the update shown from the App Store. I have since started and used XCode. Why does this update still show up in the updates list for App Store?

Is there some extra action I need to take to complete the update?

Link to screenshot: http://d.pr/i/dp3z

Was having the same problem after installing Xcode v4.6 on a system with Mountain Lion, had Xcode v4.5.2 & v4.4.1 (with different names) also installed in the Applications directory. Read on a different thread that Spotlight indices can sometimes cause problems, followed the steps outlined here:

http://support.apple.com/kb/ht2409

This fixed my problem. (YMMV)

For me this was because I had 2 different versions of xcode one in /Applications and another in /Developer/Applications

if you copy the current version from /Applications into /Developer/Applications overwriting the old version that's there, it should disappear from the updates section when you restart the App Store.

I believe this issue was caused by upgrading from Snow Leopard to Lion.