I am a new owner of the Nokia N800 and like many others, just want to upgrade my firmware, only to encounter repeated failure. After scouring the threads here, I have tried to follow the instructions using the GUI 770Flasher and the latest Nokia image on both a G3 and G4 and OSX 10.3.9. The program seems to launch fine and I connect in update mode. On both systems I receive the following message: Error claiming USB interface. No such file or directory. I have not attempted the command line method as I have no skills with this and have never even used the terminal.
On my husband's Toshiba with Windows XP, the download wizard opens fine, but when the download begins, the time to download shows between 2,000 and 4,000 minutes to go even though we have high speed internet. So here I am, in the ranks of my fellow update failures, hoping for some words of wisdom!

Does one perhaps need to run as administrator with the 770Flasher? I haven't tested it on a regular account.

For what it's worth, I have successfully flashed my N800 using 770flasher on OS X...after I realized that I need to turn on N800 while holding the Home button down. I was using 10.4 at a time though.

Maybe it would help if I upgrade to 10.4. I have been slow to do this because everything works so well. You know, don't fix it if it isn't broke!

No guarantees, but you could use the command-line flasher. It's fairly simple if you follow these steps closely

1. Create a new folder on your desktop, name it "n800_upgrade".
2. Go to http://tablets-dev.nokia.com/nokia_N800.php and enter your WLAN MAC address into the field (this is located on a sticker behind the battery panel).
3. Download the latest OS2008 release.
4. Move the downloaded firmware into the n800_upgrade folder.
5. Go to http://tablets-dev.nokia.com/d3.php and download the flasher-2.0.macosx.
   The flasher-2.0.macosx may actually download as "flasher-2.0.macosx, attachment" if it does, then rename it to "flasher-2.0.macosx".
6. Move the flasher-2.0.macosx into the n800_upgrade folder.
7. Now, open up the Terminal (it's in /Applications/Utilities/) and type:
   It will ask you for an administrator password after the second command, enter it.
   
   Code:

   cd ~/Desktop/n800_upgrade
   sudo chmod 755 ./flasher-2.0.macosx

8. Now turn off your N800 and plug in the USB cable to a port on the computer.
9. Type this into the Terminal:
   
   Code:

   sudo ./flasher-2.0.macosx -F ./RX-34_2008SE_2.2007.50-2_PR_COMBINED_MR0_ARM.bin -f -R

10. It will say:

    Suitable USB device not found, waiting

11. Take your N800, and hold down the Home button (looks like a little house), and while holding down the home button press the power button to turn it on.
12. It should start flashing and then reboot.
13. You can remove the USB cable after it has booted to a normal desktop (just make sure to eject any cards that may have mounted on your Mac).

That's pretty much it. I'm guessing that 770Flasher isn't working because your account is not an administrator, but I could be wrong. If you want to login as an administrator and try it then, it may work. If not, this method will work fine.

If you have any questions, ask away!

Well, two days later, and I finally found success! I never could get the flasher to work or the download wizard, so I had to go through the proverbial back door. I didn't initially realize one could manually update with the wizard, but as soon as I discovered this, I transferred the image from my mac to my husband's Toshiba, ran the update wizard and Voila! And wow, I'm glad I didn't give up. Thanks to all for your advice!