*** WARNING: There are 1 posts attached to inexistant category #16. You must fix the database! ***
*** WARNING: There are 1 posts attached to inexistant category #17. You must fix the database! ***
*** WARNING: There are 3 posts attached to inexistant category #19. You must fix the database! ***
*** WARNING: There are 1 posts attached to inexistant category #20. You must fix the database! ***
*** WARNING: There are 3 posts attached to inexistant category #28. You must fix the database! ***
*** WARNING: There are 1 posts attached to inexistant category #29. You must fix the database! ***
*** WARNING: There are 1 posts attached to inexistant category #30. You must fix the database! ***
*** WARNING: There are 1 posts attached to inexistant category #33. You must fix the database! ***
*** WARNING: There are 1 posts attached to inexistant category #35. You must fix the database! ***
General Support
My guess is that there are some posts attached to categories that don't exist. ;)
Did you manually edit your database and remove some categories? Did you move your database recently? Maybe the categories were lost then. When you go the categories tab, can you see that there are categories missing?
The solution is going to be to recreate your categories, then manually edit the database to assign those posts to the new categories.