Tried to add an internal link using the internal linking feature of 3.1 but on this particular client's site if you clicked on a post or page item, nothing was getting transferred up to the link/title fields.
I tried it on several of my sites which were running 3.1.2, as hers was, and the linking feature worked fine on my sites.
Finally narrowed it down to this plugin she had installed:
Custom Forms For 1ShoppingCart.com Accounts
Removing that solved the problem.