WordPress - Unable to Upload Image to Post

When uploading an image to a post, the following error message may appear:

Unable to create directory /path/to/uploads/2012/12.

To correct this issue:

  1. Log in to your WordPress Dashboard.
  2. Click Settings > Media.
  3. Check the box next to Organize my uploads into month- and year-based folders.
  4. Click Save Changes.

The issue should now be resolved.