Thread:Project:Support desk/WikiEditor toolbar icons are missing/reply (2)

Since the problem is also present in other skins, I concluded that the offending rule might be located in MediaWiki:Common.css and voila:

http://wiki.mfo.me.uk/index.php?title=MediaWiki:Common.css

contains exactly what is currently breaking the toolbar. You should change the rule in a way so that it does (at least) no longer apply to the toolbar.