Image uploading error

I am having trouble up loading images using the wordpress dashboard. I can upload images for the headers and layout etc via the FTP no problem but when it comes to inserting images into a page or post it comes up with this error message.

Unable to create directory /var/www/vhosts/copycreative.net/httpdocs/wp-content/uploads/2010/05. Is its parent directory writable by the server?

Has anyone ever had this problem before? If so how did you fix it?