After restarting my computer when I am presented with the initial login screen (the light gray one with the restart and shut down buttons), I see only two of my three user accounts.
If I log in with one of these accounts, I can see, and log in to, the third (missing) account by either:
How can I restore this account in the initial (light gray) login screen?
I tried repairing disk permissions to no avail.
If I create a new account, it does show up in the list.
Have you turned on FileVault 2 encryption? If you have, you can enable your third account by doing the following:
There should be an Enable users... button showing in the FileVault preference pane. Click it and you should be given the opportunity to enable the third account by providing the account's password.
On restart, the third account should now appear at the login screen.