1) this is now in MooTools More, so you should post questions about it in the MooTools User Group. I say this not because I don't want to be helpful, but because there's one of me here and loads of people there who can answer your questions and offer you help more quickly.
2) HtmlTable does not currently integrate with the localization. You'll have to re-author the date parser found in HtmlTable.Sort. This is pretty easy, check it out:
	'date': {
		match: /^\d{2}[-\/ ]\d{2}[-\/ ]\d{2,4}$/,
		convert: function(){
			var d = Date.parse(this.get('text').stripTags());
			return (typeOf(d) == 'date') ? d.format('db') : '';
		},
		type: 'date'
	},
I think you can figure out how to re-arrange things to match your content. Just use the HtmlTable.defineParsers mentioned in the docs to overwrite it.
I am using GB date formats dd/mm/yy but the date parser in htmltable screws up, I assume because it is trying to use the US date format. I have tried using Locale.use(\'en-GB\'); but no change. I just wanted to check that htmltable ought to pick up the locale.
Thanks for the clientcide libraries, I use them a lot and this is the only problem I have had with them.