If you go to a folder_contents page, check a content and click "Change state", you'll get a traversal error. This is because having the Subscription portlet in the site will change the request.form['paths'] variable from a list of strings to a list of unicode struings, and unrestrictedTraverse can't handle unicode.
The change happens somewhere within collective.dancing.browser.portlets.channelsubscribe.Renderer.setup_form()
A quick test seems to confirm that doing setup_form not in the __init__ but in the render of the portlet improves the situation. Possibly that's not a complete fix, but it's a start. Best of all would of course be if setup_form keeps it's fingers away from request.form. It seems like something there goes through everything in request.form and validates it or something. It's all very strange.