it happens to me too
then i had to format my whole pc to win7 ultimate *32bit*
after u connect adn press u key,
it will say
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--0x0421-0x0
105.
Found device RX-51, hardware revision 2101
NOLO version 1.4.14
Version of 'sw-release': RX-51_2009SE_10.2010.19-1_PR_MR0
Booting device into flash mode.

then it says
Suitable USB device not found, waiting.

wait for around 1 min..
u'll see the phone booting up, showing the dots thingy then it till recognize the device and emmc will be flashed