Well, this looks like an older thread and I’m just now getting this problem of ‘cannot delete posts/categories/pages’ with WP 2.3.2.
I tried deactivating all the plugins and reactivating them one at a time to see if one of them may be the reason – no dice though.
So, the only way I can solve this issue right now is to, login to admin, log out, then log back in (do the login twice). After I’ve done that, everything deletes as normal and there are no issues. I wonder if it’s a cookie related issue.
Hope this helps others out there.