When I first post a page and then modify it once, the WP cache brings me the page data when I first posted it when I try to edit it for the second time.
This is surely the problem of WP's DB caching. I found a post about this problem (http://www.zingle.net/index.php/archives/84)
Currently I have disabled the caching feature of WP. Now it works but I want to use the DB caching without the problem occured to me.
FYI, I run WP 2.0.2(clean install) on PHP 4.3.11, MySQL 4.