App store Error 100
I am running lion 10.7.5 and I am trying to download Mountain Lion 10.8, I have purchased it previously but updated to mavericks and now i am trying to go back. When i click download it either gives me Error (100) or it will turn gray and load and then do nothing and go back to being able to click "download". I have tried signing in and out, quitting app store, deleting Cache with the "Go To" folder and all that (com.apple.appstore) stuff and it still has not worked.
MacBook Pro, Mac OS X (10.7.5)