Q: Wi-fi issues with early 2011 macbook pro

I recently have some problems with my early 2011 macbook pro (running OS X Lion), when I use it on wi-fi: the wi-fi turns randomly grey and I lose my internet connection for some seconds, then it reconnects again. I would guess that it has to do with my wi-fi network, but what causes me anxiety is that the problem occurs even when I seat next to the router and once it starts, it re-occurs every 2-3 minutes, unless I restart the computer; otherwise, I may use it for hours without any wi-fi drops. Any ideas about what could cause the problem or any possible solution?

I used to have the same problem with an older macbook running OS X Tiger and the problem totally disapeared only when I upgraded to Snow Leopard!