Xcode 4.4 Mac App Store update

Recently I've updated from Lion to Mountain Lion and from Xcode 4.3.3 to Xcode 4.4. Yesterday, running the system updates, I got the following situation:

(please, see the attachment)

I've tried to remove Xcode and reinstall via MAS, but after removing and rebooting my machine, MAS insists it is still installed. I've been able to restore Xcode from a backup but I still have this problem.

I appreciate any suggestions on this.

Thanks.

 

Answering my own question...

https://discussions.apple.com/message/19081072#19081072

"The Mac App Store can see the apps on attached drives and partitions. Do you have a backup drive connected that has the older version of the app on it?"