-Update-

Well, i left my phone at the phone repair store and after a few days of examination they concluded that the hardware part is functioning fine and they want to reflash the device.

I told them that i want to make a backup first so i will take my phone, boot it up with a charged battery and perform a backup if possible.

Since they say the only solution is reflashing, after i perform a backup i plan to do it myself.
Can the the N900 be flashed from its command line and if so, how? I don't see any other options except some dedicated expensive hardware those stores might use since the USB is not being detected.

Thanks.