Here is how I was able to configure static ip address on ubuntu server 10.04 on my vSphere center at my house:
sudo nano /etc/network/interfaces
auto eth0 iface eth0 inet dhcp
auto eth0 iface eth0 inet static address 192.168.1.100 netmask 255.255.255.0 network 192.168.1.0 broadcast 192.168.1.255 gateway 192.168.1.1
Lastly, run this command to uninstall the dhcp-client
sudo apt-get remove dhcp-client
Now your server runs on 192.168.1.100 so go to your router (if you are running this at home like me) and change your port forwarding ports to 192.168.1.100.