Cannot update to Camera Raw 7.3

I want to upgrade to ACR 7.3.  When I select help > updates, I get the message: "The update server is not responding.  The server might be offline temporarily, or the internet or firewall settings may be incorrect." 

I could update Lightroom to 4.3 flawlessly.  I use Avast Antivirus, but when I disable Avast it doesn't help.