Sharing a connection with a 360

With the wireless adpter being the best part of £40 i'm having to look at a chaper method for the time being. I'm running Vista and i'm trying to use the ICS option, im connecting my 360 through the ethernet port in my pc, the connection shows up on the network but has limited access. I've tired turning on ICS for my main connection but keep getting the message "an error occured while ICS was being enabled" ive been through the services menu an set all the appropriate settings to automatic.....but i still get the same message. Have i missed somthing? :/

I'm connected to my router by wireless, which is downstairs with the modem, none of those options seem to help.

Yea i've already done the steps mentioned in the above post, still wont let me turn on ICS :S