[Plugin: WP Super Cache] file permission issue

Hi
i am having a problem with the functioning of the wp super cache mod. On activating the mod, after i have chmod wp-content to 0777, following files are created in the folder
advanced-cache.php
wp-cache-config.php
and a folder named
cache
the cache folder has meta folder, and some cache files in it and the wp_cache_mutex.lock file.
this is what it should have been like this.
Cache is not working properly. once created, the same cache is server ever if 24 hours are passed. i have looked into it and there are some problems with cache folder and files’ permissions.
the folder created has permissions 0755, group “nobody” and owner “nobody”
all the files in the folder have a permission level of 0644
I am unable to change the file permissions using ftp client. getting an error of permission denied.
Any solutions
using wp 2.7.1, php 5.2.6, mysql 5
and sorry for my poor english
Thanks