I've got the first version of the wireless adapter (G rated I think?), it's pretty shit if there is anything (walls, doors a ceiling etc) between the xbox and the router and obviously if there's quite a distance doesn't help. Other than direct Ethernet connection, Limpid's suggestion is the best and is probably cheaper than a Microsoft adapter. I managed to pick up 2 homeplugs (one needs to be connected to the router, the other to the device) for £35 off ebay. You can then just buy more homeplugs to add more devices. They're great.