Yeah I have this problem with pages. Set up my blog and created a few new pages. The owner of these pages is listed as admin.
Then I created a new user, let’s say they’re called bob, and gave them administrator rights. Now if I log in as admin and create a new page the page owner is set to bob. On the new page creation page there is a drop down menu to set the author. This has only one entry – bob.
New posts are owned by the correct author though.
I have no plugins installed.