To me, the easiest way to have a static IP address on your VU+ stb is the following:
1) log on to your VU+ STB as root with telnet or SSH
2) issue 'ifconfig -a' without the quotes at command promt and write down the HWaddr of interface eth0, this is your MAC address
3) configure your VU+ for DHCP (YES, this is not a mistake!)
4) Log on to the device of your LAN on which DHCP server runs. Most of the time, this is your Internet router.
5) Go to the DHCP server settings and map the MAC address of your VU+ STB to an IP address of your choice.
6) Save your config canges on the DHCP, restart your DHCP server and restart the network of your VU+ STB (or reboot it).
Hope this helps...