said by mark2 :
I have the same issue with my MacBook Pro 15'' running OS X 10.8.2 (12C3006). It also started behaving like this after a OS update. (But I think there has been another update in the meantime which did not fix the issue.)
Yes, they released a subsequent update to fix the Keychain issues that particular update also caused and then they've rereleased this DL1609 update to take that patch into affect. Unfortunately, they haven't noticed this particular issue. I'm working with the loser Apple engineers to admit to this problem and actually fix it. It's been nothing but hand holding I tell ya. I may need to get the crayons out for this one.