I'm having the same issue as of this morning. My client (my wife!) tried to edit her site, was able to log in, but when she got to the main content area wasn't able to edit. Clicking Edit just brings her back to the main content page (.../admin_cms/index.php). The same thing happens when she clicks Settings, Help and Advanced Search. Activity and Manage Users links work as expected.
We also don't have the Edit icons on her page when logged in to the cms.
And Log Out doesn't work, either.
Is there a fix in place yet?