yeah, you can go with tittlemouse's solution if you want...
I think there's something wrong with the ACP.
Maybe I should have a look into this
EDIT:
I think this can be a quick fix
open admpost.php go to line 360
find and replace
PHP Code:
$newthemeurl = $_POST["themeurl"];
with
PHP Code:
$newthemeurl = '/templates/'.$_POST["themeurl"].'/template.html';
At the installation process, just put the theme folder name