Internet Connection Sharing, Windows Vista and Xbox Live

I am having problems conncting to the internet/setting up my network to allow
other computers to access the internet.

I live on a boat and use a Vodafone Datacard to connect to the internet (3g
Network) the datacard is connected to my windows Vista Premium Laptop and i
can access the internet on the laptop fine.

My Main Problem is: When i connect my xbox to the laptop via an ethernet
cable my xbox cannot connect to xbox live, My vista laptop can see the xbox
on the network yet will not allow it to connect to the net. I have followed
all the ICS tutorials in windows "help and support" but to no avail.

My second problem is: when i set up an ad hoc intenet connection between my
laptop and pc (wireless connection) similar to the xbox problem my laptop can
see my pc and visa verca but again no connection can be made form my desktop
pc to the internet (Desktop PC is running windows Vista Ultimate).

All this used to work when running Win XP on both machines but i cant
understand why it isnt working now?

"Xbox live calls me, i need it!"

Any Ideas?