[support] Failure to unpublish

I have encountered a strange problem in Drupal 6. I can't create nodes that remain unpublished (through deselection of the "publish" checkbox); nor can I "unpublish" a published document by selecting and unpublishing it in the content list. When I give the command, I get a successful update message, but the item remains "published." I have user/1 privileges. I think it cannot be a privileges issue. Am I missing something obvious? Steve Hays