error uplaoding image

I get this error when I try to uplaod an image…

“Unable to create directory /usr/home/fatvine/htdocs/blog/wp-content/uploads/2006/12. Is its parent directory writable by the server?”

The jpg file that I am trying to upload is .5 meg and I have uploaded images successfully before

Anyone have any idea what could be going on or anything that I could try?