When the Security prefs pane is set up to require passwords upon wake, and multiple users are logged in, a user performing the "Switch User" function in the wake from sleep password dialog box experiences a faulty sleep event approximately 30 seconds after waking the computer -- even if logged fully into their account.
Below is the sequence of events.
1) Have at least two users set up on your machine.
2) Go into System Preferences under Security and make sure the Require password to wake this computer from sleep or screen saver is checked.
3) Log into one of the account particularly the admin account.
4) Put the computer to sleep....wait 5 to 10 seconds
5) Wake it up.
6) Click on the switch user button and logon as another user
The computer just falls back asleep again after about 15 seconds.
Thanks for an help