Remove the battery, connected your N900 to the computer;
1- Enable R&D mode: flasher-3.5.exe –-enable-rd-mode
2- Cold flash with your Fiasco Image: flasher-3.5.exe -c -h RX-51:<hw_id> -F <FIASCO image> -f (The code "RX-51" used in the example is the product code for the N900 device. The <hw_id> is the product HW revision, which is a 4-digit code. Both product code and HW revision can be found from the type label of the device to be flashed. The type label is on the back of the device, underneath the battery. )
3- Disable R&D mode: flasher-3.5.exe –-disable-rd-mode
4- Insert the battery and reboot
.....
this was found in a thread describing Mk II protocol..
should i try this ?