The only change with respect to remote monitoring in 3.5d is that now it starts 10-20 seconds after the miner starts but otherwise it should be working fine - we are using it 24/7 on our test rigs without any problems. From our own experience, this problem is perhaps related to Windows Firewall, which blocks the CDM port for the executable of the new version (it should show you a pop-up window, asking if you want to open the port the first time you start the a new version of PhoenixMiner). Another possible reason (again related to Windows Firewall) is that it may "decide" that the local network is "public" instead of "private" and it has much more strict rules for public networks, so it again blocks the CDM port of PhoenixMiner. A quick test to see if the Firewall is the culprit is to turn it off for a short time and see if the remote management works.