this is the type of button I'm using and the lightbox which it opens


By disable/enable, you mean in the "advanced actions"?
that would mean that for each button, I have to add the action to disable the others buttons, then on the popup closed button, add the advanced action to enable the buttons, right?
Knowing that I have 10 buttons, I'm looking for something easier. In Storyline, there is an option to actually hide what is below an object and by hiding is meant: you don't see it anymore and you cannot click on it anymore. I'm looking for something like that in captivate.
Thanks!!
Captivate and Storyline are two very different animals. The specific function you like in Storyline doesn't currently exist in Captivate (though you are free to log an enhancement request for it if you want).
With Captivate you can group items together and then HIDE the entire group in one go via an Advanced Action but if you want to disable interactive objects you DO need to specifically disable each one via a line in the Advanced Action, Conditional Action or Shared Action that you are using.