Thanks for your time.
I've read that article (good one, let's say...) but you're right, no mention of my error.
Strange thing: Apple Portugal doesn't either. (that much is normal I know my country.....unfortunatelly): bring the machine in and we will tell you!!!
And a land line phone to Apple USA, will cost me too much.
The stranger thing, I work with Logic Studio Pro (not a "light" work...) and never had any problems working.....
Again, thanks for your answer.