Wordpress and uploading images: is the parent directory writable by the server?

[The Salmon Of Doubt]

So, I'm tryin' to add images to my posts, but I cannot upload any [directly from Wordpress]...

Here's what it says:

Warning: is_dir() [function.is-dir]: open_basedir restriction in effect. File(/) is not within the allowed path(s): (/home/USERNAME:/usr/lib/php:/usr/local/lib/php:/tmp) in /home/USERNAME/public_html/blog/wp-includes/functions.php on line 1746

Warning: file_exists() [function.file-exists]: open_basedir restriction in effect. File(/) is not within the allowed path(s): (/home/USERNAME:/usr/lib/php:/usr/local/lib/php:/tmp) in /home/USERNAME/public_html/blog/wp-includes/functions.php on line 1737

Warning: is_dir() [function.is-dir]: open_basedir restriction in effect. File(/) is not within the allowed path(s): (/home/USERNAME:/usr/lib/php:/usr/local/lib/php:/tmp) in /home/USERNAME/public_html/blog/wp-includes/functions.php on line 1746
Unable to create directory /public_html/blog/wp-content/uploads/2009/03. Is its parent directory writable by the server?

This is a migrated installation from a free hosting account. I've read that it has something to do with permissions, but Change Permission is a dead link in my file manager.

So... Help, anyone?

[stix]

I think I found a solution Googling:

WordPress is trying to use the wrong path, you have to point WordPress to the /tmp path instead of the one found:
http://golabs.nl/2008/10151/

As your WP is in as folder named blog you need to define the relative path as described here:
http://wordpress.org/support/topic/161778

HTH