first, I'd download a newer filemaker (trial/demo) from the filmaker site to see if it works in a supported version of your OS??
If it works - Upgrade your FileMaker version, or Downgrade your mac os (if possible)...
Filemaker 5.5 was the first version that ran on OSX.
I know that it works on OSX 10.4 and OSX 10.5.2
I do not know that it works on OSX 10.5.6