I'm having an issue where the Insert Link function in the post/page editing screen does nothing when clicking on "Link to existing content" does nothing, and clicking Insert Link after adding the link URL manually takes me to the Posts page (and the link still isn't there).
I'm working on two websites at the moment which are using child themes of the same base theme. The second one, which I started working on yesterday, was essentially a duplicate of the parent + child theme of the first one and then I have started to further customise it but only with HTML and CSS. When the issue appeared I deactivated all plugins but it still occurred.
Website 1 was running WP 3.4.2. I basically cloned that site to create Website 2, which I then upgraded to 3.5. Upon discovering the issue I reverted back to 3.4.2 and the issue no longer occurs.
Any suggestions on how to fix this would be most appreciated!