You're not doing anything wrong. By default Captivate will insert a click box object when you press the ENTER key because you can set a click box to use ENTER as a keystroke to trigger its action.
The click box is invisible to the user. So just put it somewhere on the slide where the user is NOT likely to click (or under some other object where it CANNOT be clicked) and make sure the keystroke is set to ENTER.
Thanks for your reply.
I think I was not very clear, so let me explain a little bit more.
I don't get a click box but a mouse object, you get clickboxes in the assessment and in the training simulation but not in demostration.
So the user can see it and also its effects like the visual effect or the sound.
Ah yes, you did mention you were capturing a simulation with Demo enabled. I did not read carefully enough. However, are you sure you are getting a new MOUSE object added when you click ENTER during the simulation and not a TYPING animation object? That's what I would expect to see added when you hit any key on the keyboard during a simulation capture.
Can you take a screenshot of your timeline where this object exists to show us?