I am getting a warning when open or close K2 items or categories that says "item must have a title" or "category must have a title" All of my items and categories have a title. things have been working fine this is new. How do I fix the problem?

Hello Paul,

Which version of K2 and Joomla! are you using?
Are your DB tables ok and you structure up to date?

You try optimising and repairing your BD tables and/or updating/reinstalling K2.

PS. Backup (DB + Filesystem) before doing anything.