Here is what you've got to do:
- press ALT+F2
- type gconf-editor and press Enter
- go to apps/gnome-power-manager/lock
- customize the options by selecting/deselecting
done... =)
When you have problems with your OS you can spend hours and hours googling in forums for a working answer. Here I will publish only the working solutions for my problems so that you don't have to waste a lot of precious time if you have the questions I had.