I tried Use Google Libraries on two sites. The first one has the Headway theme installed and everything works perfectly.
The second one uses Atahualpa w3tc and Clouflare with a lot of other plugins. What happens is that I can't drag and drop widgets in the Widgets page.
I don't think it's Cloudflare's fault, since it is also used by the first site. I tried to disable minification in w3tc and resetting the cache, but to no avail.
What can it be?