Keychain says "Access to this item is restricted" after upgrading to Lion
Does running the command-line version of Keychain:

security dump-keychain -d login.keychain


also fail, but with the weird message In dark wake, no UI possible?

Then part of Mac OS is confused about whether it is asleep or not. There’s no need to reboot. Put it to sleep, wake it up, and Keychain should be fine again. This happens on my MacBook Pro sometimes: I open it to wake it, press the power button out of habit, only to turn it off as it is trying to start up, resulting in weird Keychain behaviour.