If the Leopard reinstallation was an Archive and Install...
Was the proper Combo (not Delta) update to 10.5.2 or 10.5.6 or .... applied.
I have seen Repair Permissions in Disk Utility fix application startup problems.
Was it bouncing in the Dock and stopping, or did you see a splash screen?
Did you notice what was listed as loading when the splash screen for Filemaker disappeared?
Do you do monthly maintenance? I am fond of AppleJack, others prefer Onyx or other utilities.
Making a new user called TEST, logging out and logging in as TEST and ... testing can eliminate possiblities.
Damaged Font Caches can cause this behavior, there are utilities to clear these caches.
Thanks for responding. No, it wasn't an Archive and Install but an install from the disk, then several online software updates to bring it back up to 10.5.8. I tried the Repair Permissions twice but no luck. The icon in the Dock was bouncing then it just stops...no splash screen. Yes, I do monthly maintenance. Yes, I made a new user and the software works fine. I'll check out damaged font caches and see if this is it.
Thanks for responding...I'll let you know.
If FMP works in a new user, it may be a preferences (plist), cache (probably font), permissions, or kext (extension) in the original user.
AppleJack tries to deal with most of these, except the font caches that may be specific to Filemaker.