S O L V E D !!!
it’s the end of a nightmare. I finally solved the problem simply searching in the MacBook directory
HD>LIBRARY>QUICKTIME
and I compare the same folder on the iMac. In the MacBook folder there was a file that wasn’t in the iMac folder named: MXFImporter.component
I have put it in the Bin of the MacBook: end of the story. WOW!