I have only just installed your plugin. For some reason there seems to be no caching taking place. I have refreshed twice and checked the bottom of the page and there is no text suggesting that is working. I have also checked the wp-content/cache/all and the directory is empty. I have all of the options ticked and the cache timeout set to once daily.
I have BP security plugin installed and the .htaccess seems to be writable as the options get saved when I save them. The .htaccess is set to autolock though.
Can you suggest anything that I might have missed? Your plugin seems great and I would love it to be working for my site.