Main Spelling Dictionary is a file that appears to be missing or damaged.
How did you migrate your application to the new computer? Did you try copying files over or did you run an installer?
You may need to delete the FileMaker folder in your applications folder and re-install.
I used the migration assistant in the Mac OS. I didn't use the installer. I can, I still have all the disks. But is it possible to just replace the file instead of reinstalling?
It should be possible, if the file you copy from your other computer is intact and still in the correct place.