Some WordPress themes not showing in Development server

Hi all, my first post! Ive been looking for a solution to this for ages, cannot find anything so thought i would ask.

I have just installed the latest XAMPP to do some wordpress theme development and customisation. I am on ubuntu 9.10 and I followed the instructions here. Ive got wordpress running smoothly, or so i thought. But when I install some themes into my themes folder they do not show in the themes list within wordpress admin. The themes are child themes of thematic, but other child themes for the same template work fine.

With some playing around I could get it to show, but it would not activate correctly and in the theme preview I get error messages, which are

Warning: fopen(/home/kent/public_html/wordpress/wp-content/themes/testtheme/style.css) [function.fopen]: failed to open stream: No such file or directory in /home/kent/public_html/wordpress/wp-includes/functions.php on line 3598

Warning: fread() expects parameter 1 to be resource, boolean given in /home/kent/public_html/wordpress/wp-includes/functions.php on line 3601

Warning: fclose() expects parameter 1 to be resource, boolean given in /home/kent/public_html/wordpress/wp-includes/functions.php on line 3604

All these warnings point to a function within wp-includes/functions.php called get_file_data, does anyone have an idea why this might be failing?

the themes im trying to install here are, amongst others this and this