Permissions problem with sitemap generator

[preeti]

Hi all
I have bought a standalone xml sitemap generator online.I am new to webhosting and a newbie in all these stuff.I ahve followed all the instructions by the software provider, but still cant get my sitemap ready.
The error showing is

"config file is not writable: /home/mydomain/public_html/generator/config.inc.php
Datastorage folder is not writable: /home/mydomain/public_html/generator/data/"

however i have changes the permission of these files in my server to 0666 and 0777 as instructed.But when I try to save my configuration it shows the above mentioned error.
help please and sorry if i have posted this in the wrong thread.

[Thaparian]

get phpSitemapNG