MarketPress conflicts with Headway Visual Editor and Headway Features Plugin

I'm having issues with MarketPress and the Headway theme. Headway uses a 'visual editor'. Wordpress' media browser is broken in the visual editor. It is possible to upload a new image or set an image url, but browsing the media library throws and error.

wp-admin//media-upload.php?type=image&TB_iframe=true&post_id=0&tab=library might be temporarily down or it may have moved permanently to a new web address.
Error 330 (net::ERR_CONTENT_DECODING_FAILED): Unknown error.

Disabling MarketPress resolves the problem. Any advice on where to fix this?