Thank you for your post.
I am running FileMaker Pro Advanced 9.0v3 on my iMac running OS X 10.5.6, so our systems are similar. I do not crash, which I know doesn't help you, so let's look at some possibilities.
1. FileMaker Pro application has become corrupt. Uninstall and Reinstall from the original CD. This should get you a fresh copy of the application.
2. FileMaker preference files have become corrupt. When FileMaker Pro launches, it looks at the Preference files, and if it doesn't find any, new ones are created. Therefore, let's remove the Preference files. They can be found in the following locations:
Home Directory -> Library -> Preferences -> com.filemaker.pro.advanced.plist
[Note: I also have other com.filemaker......plist files, but I'm also running FileMaker Pro 10, Advanced 10, Pro 8.5, etc. Remove the appropriate file(s) ]
Home Directory -> Library -> Preferences -> FileMaker Preferences (folder)
After doing the above, try again and see if you run into the same problem. Please continue to keep me posted.