I bought my wife the iPad 2 Air last Christmas and I keep her old iPad plugged in on the end table all of the time. But whenever I pick it up to use, it always indicates the last time it was backed up - 9 weeks this time. And it says for backup it has to be plugged in, connected to WiFi, and "locked" - what does locked mean? I've even tried to back it up manually but it still doesn't work. Any thoughts? Thanks.