Before doing any of this remember flashing will reset the device and you'll loose all yor settings. If you need anything backed up, you should do it before any of this. Probably a good idea for the 770s battery to be charged as well.

This is what I did:

1 - Turn of the 770 and make sure not plugged into USB.

2 - Download the flasher.macosx file from maemo - http://www.maemo.org/downloads/d3.php?f=flasher.macosx

3 - Open a terminal window in Mac OS X and naviagte to your download directory. Issue :

chmod a+x flasher.macosx

4 - Download the new 770 firmware .bin file from maemo. Go here: http://www.maemo.org/downloads/nokia_770 Enter your 770's WLAN MAC address (see the page for details on how to find it), next accept the terms, and then you'll see a list of files ... You want the big .bin one described as Software version 0.2005.45-8

5 - Go back to your terminal window, and I'll assume the downloaded .bin file is in the same directory as the previously downloaded flasher.macosx file. Now run the following (I did not switch to root first):

./flasher.macosx -F Nokia_770_0.2005.45-8.bin -f -R

You should then get messages something like :

Found image 2nd (length 8576)
Found image secondary (length 79360)
Found image xloader (length 13824)
Found image initfs (length 1567360)
Found image kernel (length 1481728)
Found image rootfs (length 57540608)
Suitable USB device not found, waiting

6 - Now plug in the USB cable (I had the charger plugged in as well) and turn on the 770. If all goes well the terminal window will stop waiting and you'll get messages like this :

USB device found found at bus 002, device address 002-0421-0105-02-00
Found board Nokia 770 (F5)
NOLO version 0.9.0
Sending X-Loader image (13 kB)...
100% (13 of 13 kB, avg. 642 kB/s)
Sending secondary image (77 kB)...
100% (77 of 77 kB, avg. 775 kB/s)
Flashing X-Loader... done.
Sending kernel image (1447 kB)...
100% (1447 of 1447 kB, avg. 795 kB/s)
Flashing kernel... done.
Sending initfs image (1530 kB)...
100% (1530 of 1530 kB, avg. 795 kB/s)
Flashing initfs... done.
Sending and flashing rootfs image (56192 kB)...
100% (56192 of 56192 kB, avg. 647 kB/s)
Finishing flashing... done

If the 'Suitable USB device not found, waiting' message stays displayed, try unplugging the USB cable, switching off the 770, plug it back in and turn the 770 back on again.

7 - Restore any data you backed up, and enjoy a much better WiFi experience!

Cheers ... Gwaant