Hi all, i'm having this same problem and have run it on win x64, x86 and get the same errors even using libusb to install the drivers

1) Removed battery
2) ran "flasher-3.5.exe -F RX-51_2009SE_1.2009.41-1.VANILLA_PR_EMMC_MR0_ARM.bin -f"
3) press 'u' and connect USB cable, N900 starts
4) on computer

Code:
flasher v2.5.2 (Oct 21 2009)

Image 'mmc', size 255947 kB
Version RX-51_2009SE_10.2010.13-2.VANILLA
Suitable USB device not found, waiting.
USB device found found at bus bus-0, device address \\.\libusb0-0001--0x0421-0x0105.
Found device RX-51, hardware revision 2101
NOLO version 1.4.14
Version of 'sw-release': RX-51_2009SE_21.2011.38-1_PR_MR0
Booting device into flash mode.
Suitable USB device not found, waiting.

After much ado...i decided to move to a linux platform to try it out and i get the same error even while running it in sudo mode.

I have also seen the cold flash option, but it was only advised to do it if a certain boot-loader test failed, mine passed which means i do not need to continue along that path. So please what am I missing? Can anyone help?