itunes password flicker

Solution that worked for me: It would appear that if you have not signed out of iTunes for an extended period of time (in my case; easily 2-3 years) signing out of iTunes, quitting/closing iTunes and restarting the machine and signing in again to iTunes will likely resolve the issue of the flickering password screen.

To get iTunes to stop the password flickering screen you will likely need to 'force quit' (Control Alt Delete) iTunes a few times. The most forced quits for me was 5 and the least was 3 - then once you do get into iTunes sign out of iTunes. Quit iTunes. Restart the machine. Tada...

PC/64 bit (Windows 7)

iTunes version 12.7.3.46