I have a very basic machine, so I am probably way off base, but I love solving a mystery! Have you downloaded anything that might have had a virus attached to it? I know you said it acted up once at the shop, so it sounds like it is in the machine itself, but have you tried plugging it in someplace in your home other than your sewing area and sewing with it? Maybe there is something in your sewing room that is interfering with the computer, or maybe it's the electrical outlet so you aren't getting steady current? Just a thought.