I've been using thunderbird fine for years. For the last few days I've been having problems which make it unusable. When thunderbird starts it shows my email folders and the emails in the last selected folder, but the preview pane is blank. The status bar shows signs of checking emails, and the numbers next to the folders update. If I then move my mouse to click on a folder or email, the entries I move my mouse over get replaced with a generic icon and blank title. I cannot click on them, and no email is shown in the pane. The result is shown in the attached image. I cannot then quit thunderbird without explicitly terminating the process. I am using thunderbird 38.8.0 on xubuntu 16.04 64-bit.