Do you have any other languages installed ( other than the default language ) ? If yes, is this error happening
when you edit a page only in another language?
When you try to publish the page, do you get the error when trying to 'Save as Draft' ? Can you give some more information. Did you upgrade your project from some previous version? Which "Publish" option are you using - publish the page from Page Edit, or publish the page from Actions /More actions menu in the grid? Can you attach some video or screen shots, or maybe provide access to your project.
the Telerik team