Some hosting providers have problems with the default WordPress directory structure.
WordPress Error: Unable to create directory /wp-content/uploads/2009/mydir/summer/ Is its parent directory writable by the server?
In order to fix this error please login to the wordpress dashboard ( http://www.domainname.com/wp-admin ) and access the Miscellaneous settings. Find the uploads path specified, it will most likely be specified as:
Change it to read
After the first " / " is deleted, save settings, and that will fix this error.