I had some disabled users, disabled because they no longer wanted to log in and write - but they had old articles.
When doing the regular cleanup of temp files and spam in Admin - I accidentally clicked Cleanup users - BAD idea!
Disabled users got deleted, and no longer could LT display articles by that user! (especially when trying to display their articles with .../user/[username] and blog pages [.../page/x] containing articles they had written)
I would have liked to be warned or stopped when I tried to delete disabled user that still had articles...
Luckily, I could re-create the users in PHPMyadmin, finally I got the userID right, and I am still alive