Create a new Theme in Mahara?

I know this sounds silly but I've followed all the instructions on the Mahara site and my Mahara installation will NOT recognise any theme other than the default one.:confused:

I've created the folders, I've copied over the config.php from the default and I've edited it. I've put some image files into the images folders as suggested on Mahara.org (http://mahara.org/interaction/forum/...d=898#post4327) and .... nothing. :yield:

Any ideas? Anything I've not done that I have missed?

Thanks