This happened to me on my new Brother Embrodiery Machine.
Open the machine as if you are going to change the light bulb.
I found thread wrapped around a post near the "hook" as you called it.
Pull that off and look for any other pieces..........I even blew the area out with compressed air. closed the area back up gently and screwed back in place. This did the trick and have no idea how it happened in the first place. I keep a can of compressed air in my sewing area and ever so often give the bobbin area of all my machine's a little blast, along with my computer keyboard.
Katrina