Change of host and problem to upload images

Hi there,

Yesterday I changed my blog from one host to another. I followed the instructions posted in the support forum.
Now I have a problem: when I try to upload a new image, the system shows this notice: “Unable to create directory /home/imcmar25/public_html/cerg/wp-content/uploads/2009/09. Is its parent directory writable by the server?”

That is my old host. How can I change the root?