Firmware Update for B50

I have downloaded and extracted the 52-452f344c file and copied it to a FAT usb drive as instructed.
When I plug the drive into the usb port on my B50 the notification to update the firmware appears. When I confirm the update all the light on the front panel illuminate momentarily and the go out. After a short while the option to upgrade appears again. If I confirm again the process repeats. On checking the firmware version it is still 48-b0ab8739-7.
Please can you give me any advice?
Many thanks.

Read this whole thread. Lots of similar problems.