I still have a few fmp6 working DB's. I don't think it is the MacOS, but not sure. When did you last Software Update 10.6.8? Try a back up or do a Recover Files from FMP6.
Is it the harddrive? the OSX install? the FMP install? the User plists? the database itself?
Start 10.6.8 with Shift Key down (wired keyboard) - this will start in Safe Mode and the HD will be repaired. http://support.apple.com/kb/ht1455
Try opening database.
OR Download, Install and Run AppleJack - use the command line "applejack auto restart" http://www.macupdate.com/app/mac/15667/applejack
Make a New User with admin privileges in Users in System Preferences - logout, login as New User and test database.
If it works the problem is in the User Folder, not the System Library or the FMP install.
A recover of the database may help diagnose a database problem http://www.fileshoppe.com/recover.htm
Does a newly created database open and run? If so, it is likely the database and not FMP installation.
THanks Jim and David.
A bit embarrassing. I had thought that My Mac was checking for software updates automatically. Apparently not, so after I updated the software and restarted the computer, the FMP6 started working again. Woo hoo. All my recipes, wine lists, music cheat sheets, and addresses are accessible once again!