Re-install App Store purchases.


I tried to open Pages this morning and it refused, saying it can't be opened while it's updating. Huh? So I opened the App Store and, sure enough, on the purchases page it shows on the Pages line in red An error has occurred. Keynote too. The button on the right says "Installed" and is grayed out.

I found a tip to hold down the option key while clicking the button, but no dice. I restarted my Mac, reopened the App Store - same deal. I closed the store, moved the two apps to the trash, reopened the store - same. In the store's main page for Pages, it still says "Installed" and won't respond to any clicks.

Any advice?
When will I ever learn? I restarted to Recovery, ran DU to repair the system disk and permissions, restarted, and ... drumroll ... all is OK again. The error messages are gone and the apps are reinstalling.