Thanks for all of the info in this thread. We run our transparent proxy locally (smoothwall) and even after adding the ip ranges and web addressed stated in all of these posts it still didn't work (listed below). I used smoothwall to see what addresses were being blocked and found additional addresses it was connecting to and then added to our destination exceptions. I will also list these below.
65.124.114.215/32
205.197.192.0/21
205.197.192.153/32
92.42.174.150/32
208.94.120.0/21
Additional Addresses
92.42.174.150
92.42.171.162
