Can't unlock preferences - no password dialog
I've had this same issue for months. Before it was my old MBP since "upgrading" from Snow Leopard to Lion, and now again on my brand new MBP with Mountain Lion. After some digging it looks like a fairly common problem, possibly to do with CAC/ID card readers.
Anyway, this worked for me (without a reboot!). From Terminal:
sudo pkill -HUP securityd
When I did this Mail apparently lost it's connection to the security framework and started prompting me for passwords; I just restarted it and it was good to go.
It sounds as an issue either with permissions or keychains. Try repairing them both.
To check Keychains for problems just:
- Locate the Keychain Access application, under /Applications/Utilities.
- Choose Keychain Access > Keychain First Aid.
- Enter your User name and Password.
- Select Verify and click Start.
- If any problems were found, select Repair and click Start again.
This issue has something to do with authd. You can just kill or force authd to quit like this (in Terminal on Mavericks):
sudo pkill -HUP authd
(when prompted, type your password.)
Just killing securityd doesn't work on Mavericks.