Memcache admin UI causes AJAX error in Panels

I've also posted in Panels

Using Panels 7.x-3.0-alpha3 with Memcache API 7.x-0.2

When the Memcache admin ui is enabled you will get an ajax error when trying to add content to a content pane.

An AJAX HTTP error occurred.
HTTP Result Code: 200
Debugging information follows.
Path: /panels/ajax/editor/select-content/panel_context%3Apage-home%3Apage_home_panel_context/middle
StatusText: parsererror

I know people have gotten a similar error when using firebug for Drupal.

Memcache still works, but you have to disable the admin UI to make this error go away.