I exported pages & posts from one WordPress installation and imported them into another. If I search for a page, either from the admin search or the public-facing search, several of them are not found. Yet if I page through the pages in the admin panel, I can see that they are all there and they work fine. This is a problem because (A) users who search for certain pages can't find them and (B) I can't find these pages in the menu builder to add them to the menu. Also, I have tried this twice now (exporting the same database and importing it into two different WP installations) with the same result.
So, what went wrong and how can I fix it?