I have used this AC since 2006 and had very few problems. Recently downloaded some aircraft from FS.com and suddenly the 727 locks the computer when I request the knee board. Tried uninstalling both the 727 and FS 2004 and reinstalling both. with no change. I notices an "ERROR-FS9" message when I start FS 2004: Flight Simulator has detected potentially incompatible aircraft or software. File: FSSound.dll Do you want to load this software? Click No t disable this software. (doesn't seem to matter whether I clilck YES or NO. Anyone have any ideas? I'm at the point that my 727 software is unusable.