Wireless connection problem

This is with the Wifey's laptop so you all know how high this is on the Get Fixed list. The trouble with the connection is that the laptop will connect to the WiFi network at 54MBS and then with use just keeps training down until it gets to 1MBS at which point it does not work anymore. A "repair connection" takes it back to 54MBS and the whole downward spiral starts again. After playing with the router for a bit, I finally replaced my router. Unfortunately, I still had the same problem, so I replaced the WiFi radio in the laptop. Now, much to my surprise, the problem is still there. Now I am lost as to what to do next and really need some suggestions. Not only is she driving me nuts about fixing it, she is also using MY computer until I get it fixed. :HELP: