IE9 on Windows 7
After installing Garmin Communicator plugin, logging in to Connect just presents the login page again. Note username and password are correct as there is no error bar presented. I can also login to myGarmin fine. I don't know if the plugin installation is the cause of the problem.
Also I appear to be signed in. There is a sign out option in the drop down in the top right corner next to the email icon but the username next to the drop-down is blank.