I've upgraded my mid 2009 15" MacBookPro to Mountain Lion and overall I pretty happy with it. But I've run into an issue and wondered if anyone else has seen it. Time Machine seems to back-up fine but it ignores the preferences. I have it set to back-up only when plugged in it runs a back-up even when I am running on battery power. So I go into the preferences and turn if off, the icon in the menu bar is grayed out and it ignores that also and runs it's hourly back-ups anyway. Has anybody else seen this and any suggestions short of doing a clean install. I've already deleted the .plist system file but that had no effect.