Assuming you have completed the steps precisely as shown below once into your ‘User Accounts,’ then it should work.
1. Select the wanted user account under the Users tab, clear the ‘Users must enter a user name and password to use this computer’ check box, click Apply;
2. In the Automatically Log On dialog box, type your password, and then click OK;
3. In the User Accounts Box, click OK.
If you have carried out those steps as shown and it is still not working, what I would suggest is carrying out the 3 steps above again but this time put back the check mark in the ‘Users must enter a user name and password to use this computer’ check box.
Then, go through the 3 steps once again as shown above unchecking once more the ‘Users must enter a user name and password to use this computer' check box.
In effect, you are resetting the procedure from scratch.
I also had this problem but when I did what is explained above, it worked.
Try this method and see how you get on.
HB