I'm getting this error on an avatar upload on my site. I've never gotten it before and nothing was changed recently for me to begin getting this error...
Warning: is_writable() [function.is-writable]:
open_basedir restriction in effect.
File(/) is not within the allowed path(s):
Modify the open_basedir settings in your hosting account and set them to none. Find the open_basedir setting given under 'PHP Settings' area of your Plesk/cPanel. Set it to 'none' from the dropdown given there. I have shown them in the Plesk panel picture.