Wireless Usb Adapters

[monkeymaps]

I just moved to a new apartment were My friend has a wirleses router on the floor below me and allows me to use it for free. I just purchased a wirless USB adapter for my desktop (lynksis mid price model) the problem is it only seems to work like 60 percent of the time. When I search for a signal is always finds the router and says the signal is always 90%+ but then when I try to connect is says it cannot communicate with the accsess point. Other times it works fine. Also I have a Wii in the living room but it always is able to connect to the same connection. Did I just buy a crappy model or im a doing somethig wrong?