I can’t confirm what’s going on but I believe that at least McAfee and maybe other firewall appliance providers recently starting blocking googlesyndication.com in the software of their appliances. It started happening at work this week where all of a sudden Google Adsense and parts of Google Analytics were unavailable to us. When I traced it, it was all requests to *.googlesyndication.com, mostly pagead2.googlesyndication.com. Once we created an entry within our McAfee appliances to allow those addresses through, everything went back to normal. YMMV.