I have two sites on the same server with some overlapping functions. I make limited use of iframes between the sites. In most (but not all) instances, my iframes display random AACII characters. If I deactivate W3 Total Cache, all works fine. My sites are http://allticketsinc.com/ and (not yet live) http://allticketsinc.com/broadwayscene.com . The plugin is currently inactive, though, so don't go to the sites hoping to see the problem.
ANY insight would be welcome. I love this plugin and want it to work.