What about adding the cron job to the root user. It's not a great idea, but it will get around the problem?
I also find it interesting that your www directory would have only root permissions and be owned by root. Usually they are owned by an apache user or have other permissions such that apache can access them.
Edit You probably don't want to edit the crontab file directy. But something similar to the following command should work:
sudo crontab -e -u root
You may not need the -u root
but it's good so sudo doesn't confuse crontab.
Edit 2 You can change permissions with the chmod
and chown
commands:
sudo chmod 755 /path
sudo chown user:user /path
Be very very careful when using this. You can completely screw up the OS by changing permissions on the wrong files or folders. You'll probably want to add the -R option which will apply the permissions or owner recursively, but again, be very careful.