@ Paul
You received the error because you had the cn_disable_output_cache twice. The second piece of code I gave was to replace the first I gave you.
I tested it and it did work.
Lets try this. Remove all the code I gave from where you added it. Install the Code Snippets plugin. After is is installed and activated import the attached snippet. To access the import page, visit the Tools > Import admin page in the WordPress admin and click on the Code Snippets link.
After you have imported it, activate the snippet.
