Problem adding content to dynamic field

When I click on Add Content when Managing Layout for Dynamic field, I just get a long list of code that does not show when I reproduce it here.

It starts out {"command":"settings","settings":{"basePath":"\/","pathPrefix":"","ajaxPageState":{"theme":"garland","theme_token":"kOA8ByK4HQaoNhOz-olDUv6HY75QzulxyMoQ0JyaJ-g","css":[]}},"merge":true},{"command":"modal_display","title":"Select content","output":"\u003cdiv id=\"ctools-content-selection\"\u003e\u003cdiv id=\"left\"\u003e\u003cdiv class=\"section\"\u003e\u003ca href=\"\" id=\"activity\" class=\"section-link\"\u003eActivity\u003c\/a\u003e\u003c\/div\u003e\u003cdiv class=\"section\"\u003e\u003ca href=\"\" id=\"custom-blocks\" class=\"section-link\"\u003eCustom blocks\u003c\/a\u003e\u003c\/div\u003e\u003cdiv class=\"section\"\u003e\u003ca href=\"\" id=\"feeds\" class=\"section-link\"\u003eFeeds\u003c\/a\u003e\u003c\/div\u003e\u003cdiv class=\"section\"\u003e\u003ca href=\"\" id=\"form\" class=\"section-link\"\u003eForm\u003c\/a\u003e\u003c\/div\u003e\u003cdiv class=\"section\"\u003e\u003ca href=\"\" id=\"menus\" class=\"section-link\"\u003eMenus\u003c\/a\u003e\u003c\/div\u003e\u003cdiv class=\"section\"\u003e\u003ca href=\"\" id=\"miscellaneous\" class=\"section-link\"\u003eMiscellaneous\u003c\/a\u003e\u003c\/div\u003e\u003cdiv class.....