Yes I did roughly 5 hard resets on my 640 because apps are getting grayed out that are installed to my sd card then it stops reading apps from my sd card period. But I can still use the file explorer to browse the contents of the card no problem. Def a store issue I believe.
It seems like if u install a app from the old store and the new store tries to auto update that app u already installed from the old store it renders that app useless/grayed out, and uninstallable