I am having the same problem, FruitySpirit – no Save Changes button in my Widget window, except that the button is there when I first open the Widget window. The button disappears when I attempt to edit anything in the window. For example, if I want to add a Pages widget and click to add, the new widget will show up at the bottom of my sidebar list, but it will be partially covered by the gray/black WordPress bar on the bottom. The Save Changes button should be under the list, but I think it is being swallowed by the WordPress bar.
A solution to this would be great. I’m using the Tranquility white 1.2 theme by Roy Tanck, in case it’s the theme that’s causing the problem rather than WordPress.