Thanks for the response Abhilash.
I'm pretty sure that DNS is fine as I am able to perform lookups and reverse lookups for the IP addresses from the vCD server and other machines on the network. I've tried uninstalling vCD and creating a new SQL DB also but each time when the install finishes it states the correct url to use but this fails to work. I sometimes get a blank grey screen when I connect and sometimes no page at all.