Bug #1459 is discussing an issue with Apple Airport Extreme access points and 802.11n in general - for anyone with 802.11n issues it would be worth submitting more detail and/or votes in order to raise the profile of this issue with Nokia. Actually, this bug is for the N800, but the same problem might also affect the 770 even though it's different hardware/firmware.

As for the OP, I'd suggest checking for errors in dmesg (you'll need to install xterm).

If dmesg appears clean, try installing wireless tools (sudo gainroot; apt-get install wireless-tools) then run "iwlist wlan0 scanning" and see what is output - you should get a list of available wireless networks. If nothing comes back, or you get an error, it probably is a hardware issue.