Hi, I am getting this issue as well on my site wakeup-world.com
The mobile site 1/2 loads, then I get a white screen with the :) symbol in the top left hand corner.
I have deleted the plugin (including all files) re downloaded and activated. Followed http://www.bravenewcode.com/support/knowledgebase/optimizing-caching-plugins-for-mobile-use/#W3totalcache and checked twice that the settings are correct. But I am still getting the :)
ps... current the plugin is deactivated so mobile users can access my site.
Thanks in advance for any help