I had this issue, and eventually got sick of streaming Randi Rhodes while browsing N770 at home,
so, I started tweaking with my wireless router.

I don't know if it was my adjusting which wireless channel is used on my router (6 or 10 or 1...) or whether it was when I preset a specific IP address (192.168.1.120) for the Nokia both on the N770 and my router,

but whichever it was, my tweaking (3 months ago) solved the problem and I haven't experienced a dropped home wireless connection since.

DCarter