The attach the signature from a file continues to appear as my selection even though I have unticked the box and setup signature text.

I created a signature within a file and I want to switch to using the Signature text box with the account options. I have unchecked the box to attach the file, removed the file name from the field, deleted the file, checked the box for Signature text, included text and hit OK. When I restart thunderbird, it populates the file field and checks the box that I am Attaching a signature from a file. I looked in the registry but cannot find anything.