This has been going on in WordPress since at least 2.9 because everytime I have upgraded since I’ve been using WordPress (2.9) nothing short of an extremely fresh install with no mods or themes fixes it. Upgrading your installation causes this problem consistently. A google search of this problem will drag up posts from 3 years ago.
My problem is the same: I click a menu to drag/drop it and it won’t let go of my cursor. For menus this is a game-breaking issue because you can’t go into accessible mode like you’re able to do for widgets.
Any developers working on this at all? What’s the issue and what’s the fix?