If you downloaded the installer to your computer, download it again. The file could have been corrupted during the download.
If that fails, call FileMaker Tech Support directly. They do not charge for installation issues and thus, you should be able to get the help you need more quickly than through this forum.
Downloading again is the first suggestion, corrupt downloads will lead to this message.
Restarting with SHIFT key down, will boot a Mac in Safe Mode and runs a fsck hard drive repair on the boot drive.
Try the install in Safe Mode, if the error reoccurs, redownload the file.
Thanks for the response. I have actually tried downloading twice. I guess it's time to call Filemaker.