an 'fmx' file is typically a plugin but I can't find anything on ArchElement.
Can you confirm that you have a plugin that is named like that?
Wim is correct, sound like plugin..
open program files (86), FileMaker Pro 12, Extensions
-> is there something like ArchElements in this Folder?
alternatively, You can go to settings in the FileMaker app, tab 'Plugins', check for that - and disable it for testing
Did it run earlier? If yes - What has been changed?
There is such a plugin.
It ran earlier and nothing changed (well, obviously something did).
No Windows update or anything like that.
Seems that You have to deactivate that plugin and try to find the one who created it )-:
You can try to install the plugin again - if You have the original download/installer
If You test it on a different user: Does it work?