I have been researching this for ages and cannot seem to figure it out. On my widgets page for all my sites, the drag and drop function is not working. When I go to click help or screen options, those will not open either. Seems like a scripting issue on just the widgets page, as all other pages in the admin seem to work fine. I checked on WordPress.org and see that many others were having the same issue, but I could not tell whether there was a resolve. Here is one thread on the subject ... http://wordpress.org/support/topic/dragdrop-of-widgets-not-working-in-31.
Do you all have any suggestions, as I have been working on this forever without a resolve and now my entire network of sites has no widget functionality.