Hi guys -
I've had this same problem on a couple different installs, not sure what is causing it.
The Behavior/To-Do/Reports/Access tabs are all unusable because the content pane is only drawn a few pixels tall. See screenshot:
This only happens on some page types, not all. I've looked VERY closely comparing details of the page types as well as the _config.php file and see nothing relevant. The last site this happened on I had to completely reinstall to solve the issue - really don't want to do that. I just upgraded to the latest release on this site and the problem persists.
The CSS for the tab has an inline property which is being set wrong (see below). I haven't edited anything relating to CMS backend, or any core.
<div class="tab current" id="Root_Behavior" style="display: block; height: 0px; ">
So why is height being set to 0px, and where can I track down this issue?