Connecting to x-box live HELP!!!

Iv spent hours looking through the fourms, so sorry if im repeating some one else.

I recently baught the wonderfull vodaphone usb dongle allowing me internet accsess, naw i want to connect my x-box 360 to my computer using an ethernet cable, done. but im haveing a few problems:

Pc Says: the network has limited or no connectivity.

X-box says: Fails when i test the network connection on IP address.

Iv been told my vodaphone dongle wont share its IP address, am i completely sh*ft*d or is their a way around this verry annoying set back.

HELP ME HELP ME!!!! i want to play my games online.

Yeh i have a router, but that didnt help, its plugged in and the lights are green telling me that i have some thing connected, but the router says i have an invalied IP address, also.

How can i get the dongle to share the IP address. or how did you get it to connect?