See here: viewtopic.php?f=2&t=571#p2731
. I thought the instructions in the posts above and below that are fairly straightforward:
1. Download the file attached to that post
2. FTP to the WordPress folder on your web host.
3. Navigate to wp-content/themes.
4. Delete the existing "suffusion" folder there.
5. Unzip the file you downloaded. You will see a folder called "suffusion"
6. Copy the new "suffusion" folder and place it in the wp-content/themes directory.