After upgrading to 13.10, I am now getting a prompt for my gmail password every time I log in. There is no indication as to which service or application needs this information. If I enter the correct password I'm told it is incorrect. My gmail account does not use two factor authentication. The problem has only started after an upgrade from 13.04 to 13.10.
How can I prevent this prompt appearing, and/or what is doing the prompting?