JS broken in post edit area

In one of my installations of WordPress (I have 2 on the same server), all the JS in the post editor area is broken – apart from the post editor. That means I can’t drag any of the blocks about, I can’t open any of the collapsible menu items, I can’t add tags, I can’t add categories etc. I’ve tried re-uploading all the JS files and clearing my cache to no avail. If I check firebug, I see a bunch of JS errors:

unterminated string literal
[Break On This Error] this.refresh();this.floating=this.item...led").removeData("sortable").unbind(".
load-s...8034843 (line 174)
d.ui is undefined
[Break On This Error] (function(d){d.widget("ui.draggable",d...e:function(){if(this.options.helper==
ui.dra...=1.8.12 (line 15)
a.widget is not a function
[Break On This Error] true):a(this).button("widget").removeC...icon-secondary ui-button-text-only"),
ui.but...=1.8.12 (line 22)
c.widget is not a function
[Break On This Error] e.removeClass("ui-dialog-disabled");br...d,arguments)},_size:function(){var a=
ui.dia...=1.8.12 (line 34)
a.ui.dialog is undefined
[Break On This Error] (function(a){a.ui.dialog.prototype.opt...this._trigger("refresh")}})})(jQuery);
wpdial...0110528 (line 1)