FAQ/Fusion and Quicktime 7
From VFXPedia
Installing early versions of QuickTime 7 will cause Fusion to crash on startup. This is caused by a bug in QuickTime 7.0.0 through 7.0.2. Apple fixed the problem in QuickTime 7.0.3, which was released on Thursday, October 12th, 2005. To prevent Fusion or DFX+ from crashing on startup upgrade to QuickTime 7.0.3 or later.