I'm on Mac using 3 browsers (Netscape, Opera and Safari)
Using WordPress 2.3.1 RC 1 and a K2 theme.
Since the update from WP 2.2 to WP 2.3 I can't drag/drop widgets anymore (in the widgets menu under presentation) nor using the sidebar manager in my K2 theme.
I wrote about the issue in K2's Google Code, but since (I) they find out it wasn't a K2 related problem they stopped helping me (which is logical in a way), the link to the discussion is here:Once on that page, you'll be able to see all the error messages I'm getting (Firebug).
The problem still occurs even after cleaning up my WordPress Folder (but the /blog/wp-content/uploads/ folder) with no plugins and themes installed...