Unable to create directory... Is its parent directory writable by the server?
This error can be received after a WordPress update changes a setting. To fix the issue please do the following...
Access your WordPress administrative area.
Click "Settings".
Click "Media".
Under "Uploading Files" there are two text boxes to add addresses to direct file uploads.
In the first address box change the following line...
home/<username>/public_html/wp-content/uploads
to the following...
wp-content/uploads
No need to change the second box.
Click "Save Changes"
That's it! Try uploading a new media file now.