Permissions probs after installation (Help!)

The installation process has gone smoothly, and then I select 'Define Pages Editor' under tools and select a file to edit (define_main_page.php for example).

The text editor comes up, but I get the following message:

Error: I can not write to this file. Please set the right user permissions on: /home/reverse/public_html/catalog/includes/languages/english/html_includes/classic/define_main_page.php

I've tried changing the permissions to 755 and 777, but with no luck.

If anyone could help me with this I'd be very grateful.

Cheers.