Pages Deleting!!!

I have just upgraded to 2.3*

Now whenever I edit a page it deletes one!!!

(my theory: it is deleting the page with the lowest ID, because I edited a page and that page itself was gone (it had the lowest ID). When I re-created the page then edited it, the NEXT lowest ID page was deleted! [it doesn’t seem to delete pages when I create new pages, just when I click “save” after editing one])

Help, please?

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* This may not be significant, but I never had this problem with the older version…