I'm running WP 3.0.1, on a site I launched about two months ago. I tried to open one of my sidebar widgets tonight, to change something, and it wouldn't open. I then discovered that I couldn't drag any widgets, either. Suspecting a possible conflict with a plug-in, I deactivated them one at a time, but no luck there. Here are the plugins I have activated:
AddThis Social Bookmarking
AVH First Defense Against Spam
Google XML Sitemaps
Simple 301 Redirects
Tweet Meeme Retweet Button
W3 Total Cache
Wp Security Scan
It's been a couple of months since I had occasion to go into my widgets, so I have no idea how long this problem may have existed. Everything is functional, but not editable.
As a point of interest, I originally started out with the Display Widgets to set my widget displays by page, and about a month ago, had changed to Widget Logic. I didn't like it, however, so I deactivated it and returned to Display Logic.
My site is http://docsheldon.com.
I'd really appreciate any advice you may be able to offer.