Windows 7: Windows 7 MCE and Xbox 360 setup

I bought an xbox 360 the other week with the intention of using it as a media centre extender upstairs. My PC is downstairs and both PC and Xbox are wireless. I have the 'N' wireless adapter for the xbox but my router only supports 'g'.

When I initially setup up the xbox and pc for use with media centre it all connected fine, but gave a warning that because both the pc and xbox where wireless it might not work that well. It didnt, so I now have my pc connected to the router with a cat5e network lead. I have disabled the wireless card on the pc and tried to use the xbox again, but whatever I do it wont connect to the pc. As soon as I enable the wireless card again it connects straight away!! Its really annoying!!!

I've tried deleting the settings from both pc and xbox and starting again from scratch but it still doesnt work!

Can anyone help?

Thanks