I've not switched the card into another machine mainly because the other machines use wireless B cards not G and I didn't want to go through that hassle. I spent some time out on Linksys support site and just disabled MAC filtering. Prior to doing that I noticed if the notebook was right next to the router I was getting throughput. If I took it to the kitchen even with an excellent connection the throughput seemed to go to a crawl or to nothing at all. As I write this response I'm sitting next to the router. After I post this I'm going to try other parts of the house and see if disabling the MAC filtering helped. Our other computers work all over the home with no problem. Hopefully this will be resolved. I'll let you know.
Don
Don