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The first thing I would try is deleting any preference files associated with Fireworks.
 
user > library > preferences > Adobe Fireworks CS4. Move that whole folder out to your desktop and then try launching fireworks. If it doesn't solve the problem, just put it back. (Fireworks should regenerate a new copy of this folder when you relaunch) If it does, you can delete the files from your desktop.


This assumes it's in the same place as CS3.
 
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