Help with Wireless and telewest !

Hi can anyone help me out here

What i have set up is a telewest cable modem going into a d-link wireless
router, i have the main pc downstairs wired via ethernet and the upstairs pv
connecting via wireless usb device. At first i couldnt get the router to
connect to the internet, i eventually got connected by using the router
wizard to set up the connection and this cloned the mac address , after this
i was able to get connected downstairs.I then set up the wireless device to
connect using wpa security. It was connecting at 1st now the problem i have
now is i cant connect to the internet upstairs unless the downstairs
internet is on, and now i keep getting the page cannot be displayed error
upstairs even though it says the network is connected and the signal is
good.

anyone any ideas on
1)why i need the downstairs internet on to connect upstairs
2)why i am getting the page cannot etc even though network is showing ok

cheers
Rosco