I thought I'd bring this up as my question is somewhat related. I've noticed the same situation although something else might be going on.
I've got the SD card on my Windows 7 (64 bit) machine and I can see all of the directories shown under "Preparing the Image" here:
However, I cannot see the "boot" partition of the SD card. My system says the card is only 511 Meg and I know that is wrong since it's an 8GB SD card. It seems the boot partition is hidden (or something) so I can't see this "README.txt" file either since that is where it is supposed to be located. Consequently, I can't do any kind of "preparing" since I can't get to the files in the boot partition. What gives?