Just found this in a brand new installation of 1.5.2. To reproduce this bug:
* Go into your admin panel.
* Click on the 'Manage' top level menu.
* Then click on the 'Pages' sub-menu.
* Then click on the 'Write' top level menu.
You'll see the wrong sub-menu is then highlighted: 'Write Page' is highlighted but in fact you are on the 'Write Post' menu (at post.php).
Anyone else confirm this?
Note: It also occurs in 1.5.