Why can't I connect to my wireless repeater by ethernet?

I have a wireless repeater that has a high gain antenna fitted to it to pick up my neighbour's network, which we use to share broadband. When I use my PC's wireless card it works fine, but the speed is greatly reduced (as you'd expect with wireless) so I'd rather connect to the repeater by ethernet. I have done this successfully and got a full speed connection, but only when I set it as a bridge that makes a non-wireless device (such as an xbox) wireless. As soon as I set it up as a wifi repeater the ethernet won't work at all. Any ideas??