I have upgraded a Mac Book pro to OS 10.9. The device is used on a network which has a proxy server in place. Before the upgrade to 10.9 Safari worked fine and all other Macs running 10.8 or less (about 200 of them) work OK. Since carrying out the upgrade Safari does not connect, it just hangs with no error messages. I have loaded Chrome and using the same proxy settings that are in Safari it works fine. Is this an Apple 10.9 bug?