This is a common error received by the Adobe Fireworks CS4 users.
If you're using Windows XP, you need to go at [Drive C:] > Documents and Settings > [username] > Application Data > Adobe > Fireworks CS4 > [language] and delete Fireworks CS4 Panel Prefs.xml file.
If you're using Windows Vista, Windows 7 or Windows 8, go to [Drive C:] > Users > [username] > AppData > Roaming > Adobe > Fireworks CS4 > [language] and delete the same file.