If I understand correctly, you are using WP 3.1 RC-5. Which version of Dynamic Widgets are you using?
Since WP 3.1 the jQuery library has been upgraded which implied an upgrade of the base jQuery UI library also. Result was I have to upgrade my JS scripts also. So, when WP 3.1 is officially released, a new version of Dynamic Widgets will be released also. Until then there is already more or less support for WP 3.1 in the development version of Dynamic Widgets. Trouble is, you won't see it because WP 3.1 is in RC. Result for that is a JS error in the edit widgets page not able to use the accordion. When WP 3.1 is released and installed AND the current development version of Dynamic Widgets is also installed, the accordion starts working correctly.
I haven't looked to this Google CDN plugin. Not sure if the plugin takes the jQuery upgrade for WP 3.1 into account. When the plugin does not take versions of jQuery / jQuery UI into account by the version used for WP, I think this should be fixed by the Google CDN plugin author.