[Plugin: Widget Wrangler] Widget assignment menu does not pull down in FireFox

I have Widget Wrangler functioning 100% perfectly and responds exactly how it is supposed to in IE, Chrome, Safari, and older versions of FireFox. However, in FireFox 18.0.2 it works 99%, which is to say the one (and only) place it does not work is when I go into either pages or posts and try to assign a widget to a sidebar. It drags OK but the little pull-down menu does not open. Again, this is only in the most recent version of FireFox. FireFox Release 12 works just fine.