Endless prototype.js error in Dashboard

In Firefox 2, when I try to drag widgets to the sidebar, the hand icon shows up but does not actually drag anything. Meanwhile, my Firebug Javascript debugger goes nuts and racks up thousands of errors. I have taken a screenshot of it in action:

http://farm2.static.flickr.com/1087/530751682_7d0f522b44_o.png

In Safari, the widget area looks like this:

http://farm2.static.flickr.com/1104/530871493_6ca930ac06_o.png

and I can drag NOTHING.

This is obviously a prototype error.

I also cannot switch between code and visual editors when editing (I can only see the visual editor), and I get the famed “Are you sure you want to navigate away from this page?” popup after I write a post. In Safari, I can actually publish a post, but can’t get to the visual mode. Any ideas?

Firefox publishing error: http://farm2.static.flickr.com/1018/530861441_6ef6074c6e_o.png

Firefox publishing javascript error message:
http://farm2.static.flickr.com/1197/530751668_0ea716ea6b_o.png