About two days ago, Thunderbird started acting dumb. Whenever I open it, all I see is a blank screen in the area where I'm supposed to see the subjects of my emails. And I can't see any new email either. And I noticed it has started saying "Building summary file for Inbox" at the bottom. Never saw that before. However, I can still see the emails in my Sent folder and my other folders inside the Inbox. Any ideas? Using the latest version, if that helps.