It was confirmed that both Global Directory and HTTP services, from either the Cisco IP phone or from a Windows workstation, does not work.
This situation can be solved in the same manner that you would troubleshoot a web server that is down (which is actually what is going on). Since both Global Directory and HTTP services are down, it can be concluded that the web server that is hosting these two services is not working. In this particular instance, there was a change in proxy servers.
The phones and browsers in Windows workstations had the old proxie's IP address still cached. A reboot and clearing of temporary files solved this issue.