If a user account is locked out due to invalid password attempts, the user account's user icon in the tree and the user account's General tab both indicate that the account is locked. The icon in the tree has a red-circled X on it and the General tab's Statistics area indicates the date and until which it is locked. (You may have to refresh the interface to see the changes.)
You can change the lockout time on the Settings Template's Security tab in the Login Security Options dialog box.