first - is it Windows or Linux machine? I assume it is Windows (you mention agent deployment), in this case agent deployment uses SMB, i.e. being able to connect to the machine is not enough to dismiss network/firewall issues. Have a look here for the ports required: http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1010056.
Also note that:
simple file sharing ('sharing wizard' in recent Windowses) must be disabled at the source machine;
you should connect as administrator to the source (i.e. the source machine must allow administrator to connect remotely)
If you connect by machine name instead of IP, check whether your DNS resolves it correctly.