I’ve been getting this same thing with my development version (local hosting) on which I create themes and test various things. Haven’t dared to upgrade my online version after noticing this behaviour.
This began after upgrading to 2.5, and I did everything said on the upgrade guide(s).
But I can see it definetly is something caused by the permalinks. When using “(possible /index.php/) category > postname”, no pages display. But when switching to “year > month > day > postname”, pages work flawlessly. Tried with two databases, and the other database was a backup before the 2.5 upgrade.
It’s good that it works with some kind of a permalink structure, but I’d prefer the “category > bla” instead of a “date > bla”. :/