Thanks for posting!
I haven't seen this behavior before but it sounds like a possible font issue. Do they have fonts in the /Users/<username>/Library/Fonts folder? If they do, try moving them to a folder on the desktop and see if the issue still occurs.
It might also be a good idea to remove the FileMaker plist files. These can sometimes become corrupt and cause unexpected behavior. Head to /Users/<username>/Library/Preferences and remove any plist files that begin with com.filemaker.
Thanks, I will give that a go and see what happens!