Listed below is EXACTLY what I have done (using Linux Mint 8 amd64), and it works flawlessly. Please keep in mind ALL of this info I picked up from Maemo.org.

Before you begin: please read every last word of this post and get a good idea of what all is involved before you get stuck.

This is my very first "help" tutorial. Please understand that this is the only way I can contribute to the "Linux" community, and it is limited at best.

ANOTHER IMPORTANT NOTE: BACKUP BACKUP BACKUP!!!!!!

This procedure will get you started from scratch, this will in turn save you a lot of heartache in the end, if followed correctly.

Also note, if you are NOT comfortable doing this THEN DON'T. If you are unfamiliar with this type of procedure... THEN DON'T DO IT.

Not to sound rude but this is the only way to put it. Thanks in advance for understanding. BTW, I am a noob too, so use these instructions carefully.


BEFORE FLASH: (See resources at the end of post)

Backup,
Then, write down ALL of your repositories (application Catalogs) here are mine:

Maemo Extras
http://repository.maemo.org/extras/
fremantle
free non-free

Maemo Extras-Testing
http://repository.maemo.org/extras-testing/
fremantle
free non-free

Maemo Extras-Devel
http://repository.maemo.org/extras-devel/
fremantle
free non-free

Xiaoka Maemo Extras Repo
http://codex.xiaoka.com/apt/
left blank
free non-free



Install maemo flasher on host machine (assuming you have linux and it (flasher) is not already installed)
(for amd64 linux mint)

Code:

dpkg -i --force-architecture maemo_flasher-3.5_2.5.2.2_i386.deb

Power up n900 while holding u key (while Powered off, plug in usb cable while holding "u" key)


Change directory (to directory where flash image is located)
e.g. cd /home/users_name/desktop/


FLASH: (in terminal on host machine type/paste the following)(this step is optional)

Code:

flasher-3.5 -F RX-51_2009SE_1.2009.41-1.VANILLA_PR_EMMC_MR0_ARM.bin -f

DO NOT REBOOT YOUR DEVICE!!!! If you do the above step
(This step is optional as it removes EVERYTHING, e.g. settings and the like. If you did, backup,
it will be safely stored on your sd card, which is NOT effected)

Code:

flasher-3.5 -F RX-51_2009SE_3.2010.02-8.002_PR_COMBINED_002_ARM.bin -f -R

(-R = reboot when finished)

AFTER THE FLASH:

Install Sixaxis
(Follow the instructions on the Developer's site EXPLICITLY)

Reboot
Then proceed to the next steps.

RESTORE FROM BACKUP:

Restore apps,
Next Contacts,
Finally Settings

-END-

I was having the same issues as everyone else. I then decided to do the procedure above with no problems.

Thanks Smoku for writing this program.

Please feel free to modify this list as necessary for ease of use.

Resources:

Flashing instructions
Sixaxis Developer's Instructions