Was playing with Vista, and at first things were okay, and then after a while I noticed that megatexture and saved rendition files weren't showing up in their respective folders.
Apparently Vista really doesn't like apps writing to their own program folders unless you're running an app as an administrator. Otherwise, it tricks the app into writing and reading the files from a totally different folder.
Leveller is going to change to write such data to $user/My Documents/Daylon Graphics/Leveller/$ver/... or some such.
Ray