A few days ago, I was having a problem with a long load time for a popular page of mine and the W3 Total Cache plugin developer suggested I move to the development version. I did, and then while it worked, I had tons of complaints on the response time. My monitoring service since then has said my site is down most of the time, except that is really not down at all. In addition, my Adsense revenue dropped a good bit.
My only guess is that the response time has worsened to the point that the monitoring service gives up and calls it an outage, and users give up and leave the loading page before clicking adsense. The weird thing is that the response time doesn't seem that bad when I try it. You can try it at http://www.ihatethemedia.com.
When I upgraded to the development version, I deactivated the current WTC plugin and renamed that WTC plugin folder on the server. Then I uploaded the development version and activated it. I set the settings to the same as it was in the previous install. I use memcache and MaxCDN.
Anyone have any idea why this might be happening. Could it be that it's because the cache is empty to begin with and it's been having to build a lot of cached pages for the first couple days after installing the development version (we have 5,500 posts and 10-15K visitors a day)?