I also have unstable wifi connection (reported to Nokia). I think that the problem is the opposite of what people think, however. My 770 has very, very high sensitivity. Much better than my powerbook, for example. So it picks up more networks, and presumably more interference.

At my home my 770 detects at least 4 networks and I have unstable connections. If you have stable connections, how many networks does your 770 see?

Another possibility is that I have a problem with WPA-PSK. It works (on my Netgear router), but maybe this is the reason why the connection is unstable.