I used to be able to click on and drag the vertical border between the Mail Pane and the Calendar Pane left or right to make one page wider and see less of the other pane, and vice versa. Something happened today and I can no longer drag and adjust width of the calendar pane. I can do it between all other panes to the left. But the calendar pane is in a fixed position on the right side of my screen and seems to be a fixed width. Any idea what I might have done?