I was on the general FSX forum in AVSIM when I found this topic http://forum.avsim.net/topic/313737-can-someone-help-me-with-the-pmdg-747x/ I don´t have a clue about his problem so I wrote for him to show up here. Someone could help?

Try uninstalling the 747. Then in your airplanes folder remove anything left that is to do with the 747 them try a reinstall.