Question:

Ric writes: After upgrading my Mac from Snow Leopard to Lion I discovered a problem with the Mac App Store. My “Purchases” and “Updates” categories are not updating to reflect which applications I have installed and which need updates.

For example, when I click “install” to update apps, the update completes but the app and its corresponding update are not removed from the “Updates” list. The same occurs on “Purchases;” when I click “install” to install a previously-purchased app on my Mac, the app installs but the “Install” button remains on the list instead of being replaced by “Installed.”

Is there any way to reset or reinstall the Mac App Store so that I can resolve these issues?

Answer:

While there is no easy way to uninstall/reinstall the Mac App Store, it sounds like your problems are being caused by corrupted preference files. To find out which preference files are used by the Mac App Store, we used this method to locate them by their recently modified status. The files in question are located in ~/Library/Preferences/

com.apple.storeagent.plist
com.apple.appstore.plist

Quit all applications on your Mac, delete the two files above, and reboot your Mac. After the reboot, launch the Mac App Store and you should see the behavior of the “Purchases” and “Updates” categories returned to normal.