SOLVED: I encountered this again while flashing pr1.3 and the vanilla image again. The only thing I could think of is that I hadn't rebooted the computer after shutting down xfce. Since I already knew the problem was probably HAL related, I ended up killing all instances of "hal-storage-addon" (just to be safe, you may want to kill everything with "hal-storage" in the name). Once I did that, it worked without a reboot.

Next step will be a script or something to blacklist the N900 during flashing operations, although killing the HAL storage monitoring daemons seems just as easy if not easier--it's not like we're flashing every day, right?

For Windows 7 users:

Go to devices and printers. Locate the N900. In my case N900 was listed as being in PC Suite Mode. I then right-clicked and clicked solve problems. After Windows had finished solving problems the flasher detected the N900 and began flashing.

OK TRUST ME, I've tried almost everything.

Option 5 in this link works for any issues with USB not being detected
The best solution for this is here and use option 5
http://wiki.maemo.org/Updating_the_t..._Windows_7_x64


WINDOWS 7 x64 that is

guys.. just after going through ur conversation
i was also facing the same problem since i flashed my n900 with the latest firmware from there original site. it was of the Indian region..
i flashed it 30 times... but still it gave me error in flashing emmc ...

what i did ws. i downloaded the latest global firmware instead of the Indian one ..
and then when i tried to flash my emmc. it ran successfully..
i recommend to get Global firmware
and flash it first without "-R"
then after that without booting the device flash the emmc.
im sure it will defiantely wok..
i replied coz u people only helped me to flash it.
thank you to all and.. hope my methode will also help ..