Since I upgraded to WP 2.3, I have a rather annoying problem with pages. When I use HTML entities for special charachters (I use < and > a lot) the next time I edit that page, all those characters are there in plain, i.e. the HTML entities are gone.
So say, I insert & lt;span& gt; (without the spaces) in a page and then save it, the next time I want to edit it, it's converted to <span> somehow. As long as I don't save it now, I'm alright. But once I do, all my HTML entities are gone and conveted to the plain character they represent.
Peculiar enough, this does not affect posts, only pages. It happens on both my production site as my local test installation. Even on a clean, fresh installation from scratch, so without plugins, custom themes or anything like that.