Default tab has no message pane and doesn't keep focus

On opening postbox, i get a blank message pane, and the tab bar has the rss icon and the title "26d04e3a". The message pane acts normally once an account is selected, and i can still open messages, but when i return to this default tab from a message it is blank again and the focus is on the rss account. The only way i can read messages is to make a new tab, which then acts normally.