SharePoint Designer tends to behave itself and function as well as it is supposed. That is until yesterday. In the contents of the Lists and Libraries tab for the main/top level site shows nothing. There are supposed to be a whole bunch of lists and libraries there, but instead it only shows a message saying, "There are no items to show in this view." It's a similar situation for the Workflows tab as well. Refreshing the lists, resetting IIS and rebooting the server has done nothing to improve the situation.
The View All Site Content option in the Site Actions menu for the top level site displays all the lists, libraries, etc. All other tabs in SharePoint Designer display everything they're supposed to display, such as Content Types, Subsites, Files, etc. The Lists and Libraries tab, as well as Workflows and all other tabs for all the Subsites seem to work fine and displays everything they are supposed to display. It's just the top level site that seems to have this problem.
I'm not sure what has happened here, nor do I know how to approach this issue. Any help and advice is most welcome.