Not to rain on this troubleshooting parade, but we're missing the first piece of info here. What is your network setup? How is untangle setup? Router? Transparent Bridge? Need IP's for the network, untangle, DNS, etc. Other things that matter, are you blocking the RDP packets? do you have Antivirus software like Symantec that scans packets and blocks them as well? Firewalls? Make sure there is nothing blocking the untangle portal software from working. Try turning off the different appliances like Web Content, Attack Blocker, etc.. Just run the basic necessities, router/Firewall whatever you're using. See if it works then. If so.... Then turn them all back on one by one testing it each time till it doesn't work. Then you'll know if something is blocking one of them? Are you using a DMZ when testing this and didn't configure the racks to not scan DMZ? Too many things.. Maybe try posting a Visio like drawing of how its on your network, ip's settings, etc. so we can see if maybe there is something put in wrong. If you can't resolve host names, then your DNS is not setup correctly. Are you using DHCP? Which host names don't resolve? Local or internet?
Sorry for all the questions but it makes a difference on troubleshooting and none of this was mentioned clearly above and I fear everyone is troubleshooting seperate segments of problems that are similar but with possibly different solutions.