Macbook Pro won't accept user name and password


I'm working on a Macbook Pro, OSX 10.7.2, 2.4 ghz Core 2 Duo, 4gb RAM, 250 gb hard drive. Shut the computer off yesterday as opposed to putting to sleep. Today, instead of the usual opening boot screen with multiple users, I see a gray screen, apple logo in the middle, with only one user name and password request. No user name or password that I know is good, works. Any suggestions?
I got into disk utility by holding down the alt key during startup, but don't know how to proceed to unlock the computer. How would I load 10.7.3 into a password locked computer?
alt key?

reboot your MacBook Pro to the recovery partition by holding Command-R during a restart.
You can reset a firmware password (if that is activated) by clicking the Utilities menu/Firmware Password. If the next window asks you to Activate the firmware password, then you don't have one. You can then quit that utility, then open the Terminal, and type reset password, and press enter. That will bring up the password utility. Choose your drive, and select the user name, and you can change the password for that user.
But, I more suspect that something else has happened, and you might want to quit that password utility, then choose Reinstall OS X, and continue with a reinstall of your system.
You need an internet connection to do this. This reinstall will (probably) not lose any of YOUR files, and should simply reload your Lion system.
Holding command-R didn't help. It went right to that weird start-up screen, asking for user name and password, showing battery strength, clock and the airport icon, and giving me the option to sleep, re-start or shut down. Will try your suggestions and see what happens - thanks!!
This article should help.
You'll notice that it specifically mentions your problem, which probably means that you are not holding Command-R soon enough in the boot.
Some folks ask "how soon is soon enough?"
If you hear the boot chime sound end, that's probably too late to hold Commmand-R.
Shutdown, then press and release the power button, and then immediately hold Command-R. Don't wait for the boot chime.
It's telling me my recovery drive is locked. How do I unlock it?

What indicates to you that the Recovery drive is locked? Is "Recovery drive locked" actually the message that you see?

That may simply be another symptom that your hard drive is failing.
it may mean that you have a firmware password, which would NOT ask for a user name, and you would only see a simple password block, with a padlock on the left side of that password window.

Is that what you see?