Error with Zen.

"The popup content area for this theme is misconfigured.
There is no element that matches "div.left-corner > div.clear-block:last"
Go to admin/build/themes/settings, select your theme, and edit the "Content Selector" field"

Is the error I encounter when saving an edit while using the zen theme. Not sure exactly what to think about it, but my theme seems to work fine otherwise so I'm assuming the problem is within subedit.