[Fizzlemizz]

Every time it's shown you run listview_CreateList

Every time listview_CreateList is run, among other things, it creates a new fontstring on the buttons so you are getting overlay.

Maybe change your xml to only create the buttons, fontstrings etc. once, or do it OnLoad.

<OnShow>
	self.selected = nil
	if not self.buttons then
		listview_CreateList(self, self:GetHeight()/20)
	end
</OnShow>