You may have interference or a weak signal. Do you have a wireless phone using the same frequency band? You can change the xmit channel on the router - this may fix the problem. Try using the laptop in the same room to test if it's a signal strength problem. If it's an old house with plaster walls you can have signal problems. Try to place the router at max distance from the downstairs computer and without any metal between it and your laptop. You could try a replacement antenna for the router (that helped in my case).