Can you see HTTP packets from your IP Communicator reaching CM?
Go to CLI and take a packet capture:
utils network capture eth0 file HTTPServices count 100000000 size ALL
Then download the packet capture through RTMT (if you want to see more details about this task check this post), the option you want to check in RTMT is called Packet Captures.
Filter the captures by IP address of the IPCom, if you see the request coming into CM then you might want to packet capture your PC and make sure the HTTP responses are there.
Go ahead and uploadthe packet captures if you want, specify the IP addresses and I might be able to tell you whats going on.