When it comes to speeding up the loading time of my Joomla sites, I'm a big fan of the extension JotCache. (To see how JotCache does this, check out this JotCache video tutorial I made for my clients whose sites use it.)
Today I installed the latest version of JotCache to my site and noticed that my Google Ads were no longer appearing on the site. When I turned JotCache off, the ads worked fine so I concluded that somehow the Adsense codes on my site were getting a bit mangle beyond recognition by something in the update.
After looking around the settings of the JotCache area accessed under components, I checked out the JotCache plugin. It was here that I noticed that I had the "compress cached content" option on. I turned this setting off, emptied all cached pages and then visited a page on my site. The Google ads were back.
I suspect that JotCache's compressing was doubling up with other extensions I use in Joomla that compress elements of my pages. This probably resulted in things just getting too confused when it came time to decompressing and reconstructing my pages.