Hello,
Sorry to hear you are having issues. I am not on Fences 3 right now, but, from what I remember if this happened usually there is a corrupted Fences layout somewhere in your setting. What you can try is this. Delete off the latest saved layout snapshot files and than reboot. Try that and report back.
Snapshots are stored in the following directories:

Thanks
Basj,
Stardock Community Assistant.