Thank you for your post.
I am running an iMac with 10.5.6. I just installed FileMaker Pro 8.5v1 and updated to 8.5v2. FileMaker Pro then launches without a problem.
I switched my operating system to Norge, rebooted, and launched FileMaker Pro 8.5v2 without a problem.
Can you try reinstalling? Maybe install with an English system, and try it. If it works, then switch your system back to Norge.