After upgrading to Lion, my MBA starts up fine but all my documents are gone. Mail won't start up, iTunes says it is missing the iTunes folder (and I can't find it). iPhoto says I haven't got permissions to create a folder and the keyring is not working in Safari. I've got my files on another Mac, so backup is no problem, but I can't figure out how to make things work. I tried to reinstall Snow Leopard but it wouldn't allow me to install on the HD. Anyone got a good idea?