I am happy to report that I managed to successfully flash my N900. It must be the first time that Windows saves my bacon, but I successfully did this in the same computer (Windows XP SP3 partition).
I think perhaps the flasher was having some issues in my old Ubuntu 8.04 (I installed it via the deb, by the way).
Here's the procedure I followed in Windows XP SP3:
1. Install flasher via the installer (maemo_flasher-3.5_2.5.2.2.exe).
2. Put both the eMMC and rootfs bin files in the same directory where the flasher executable is stored (by default is C:\Program Files\maemo\flasher-3.5).
3. Open a Command window.
4. Go to the directory where the flasher and the bin files are.
5. Turn off N900, and connect USB cable to PC.
6. Start the flasher with the eMMC image:
flasher-3.5.exe -F RX-51_2009SE_10.2010.13-2.VANILLA_PR_EMMC_MR0_ARM.bin -f
6. Open N900 keyboard. Hold the 'U' key.
7. While 'U' key is held, connect N900 to USB, and wait until the dim Nokia logo with dim USB logo on upper right corner shows up.
8. Flashing will start. Wait until it says that the image was flashed successfully.
9. Now, take out the battery from the N900 (this is to foolproof the process).
10. Disconnect USB cable from N900. Leave the battery out for 10 seconds.
11. Now, start the flasher with the rootfs image:
flasher-3.5.exe -F RX-51_2009SE_21.2011.38-1_PR_COMBINED_MR0_ARM.bin -f
(Notice I don't use the -R option to reboot the N900 automatically, because I prefer to remove the battery to avoid booting while USB cable is still attached).
12. Hold the 'U' key.
13. While 'U' key is held, connect N900 to USB, and wait until the dim Nokia logo with dim USB logo on upper right corner shows up.
14. Flashing will start. Wait until it says that the image was flashed successfully.
15. Now, take out the battery from the N900 (this is to foolproof the process).
16. Disconnect USB cable from N900. Leave the battery out for 10 seconds.
17. Replace the battery and the back cover, and start up the N900 normally. Be patient. The first boot will take a few minutes due to system setup.
The moral of the story? If flashing fails, it may not be your N900's fault! Try a different computer, a different OS, USB port, etc.
I'm still shocked Windows triumphed where Linux cowered in defeat.
