[subprime]

I had this issue too except I didn't get an error message. The app would download but never install. I tried to unmount which worked, thank you! However, I also noticed that everything on my home screens was duplicated. By this I mean if I deleted a widget, shortcut or whatever, it would still be there. I would have to delete it 2 or 3 times before it was gone. Moving an item would result in 2...the original and the one I moved. My only guess is the dups were created when I restored my back-ups. After I got rid of all the dups and a reboot, my install problem went away.