Background: The application should launch no matter what the Mac hard drive name is. If the OS is ready to accept the naming convention on the hard drive, so should the application. However it generates the error if there is a special character at the end of the Mac hard drive name, especially a dot.
Remove any special characters (such as these: .:*?|#) from the drive name or update to the current version of QuarkXPress to 9.5.1.