changes in account settings do not save after closing thunderbird. when re opening the setting are back to previous settings.

In particular is the "attach the signature from a file check box and the file path in that field. changing the file....works as long as program is open. same with the check mark on or off....but as soon as you close the program and open it again the check mark is back on and the same old file name and path are there.....even if I delete the file completely from the computer...