The complete Mailboxes sidebar has disappeared when opening my email. I am using Version 61 and it is up to date and Windows 7. There is a small blue button in the lower left of the white box that says "loading". Then out of the blue it will sometimes pop up, but that is very rare, and only after I have had to open and close email quite a bit. Then it will disappear again when opening and show the same blue button "loading". Strangely the sidebar is there in Internet Explorer and Google Chrome. Thank you in advance for any help you may be able to offer!