This error is related to a bad SD card write.
I got this error for the first time after copying 2012-09-18-wheezy-raspbian.img to an Integral ultima PRO 32GB Class 10 SD Card.
The SD card had worked fine on many previous versions of Raspbian/Debian and is only a few months old so I didn't suspect a physical fault.
Turns out that the Debian system I used to "dd" the image to the SD card had mounted the boot partition of the old Raspbian so my dd operation was on a mounted partition.
I tried a few times to re-write the image and noticed that fdisk still thought the SD card was inserted even when it was removed.
The solution
1) Shut down the PC and reboot it with the SD card removed.
2) After rebooting, insert the SD card and use dmesg to discover what device it has been assigned.
[ 1857.197006] sd 6:0:0:2: [sde] 62552064 512-byte logical blocks: (32.0 GB/29.8 GiB)
[ 1857.197745] sd 6:0:0:2: [sde] Assuming drive cache: write through
[ 1857.200390] sd 6:0:0:2: [sde] Assuming drive cache: write through
[ 1857.200395]  sde: sde1 sde2
3) Check if any partitions have been mounted using mount and grep (change device as needed)
mount | grep sde
4) Wipe the partition table on the SD card as per
5) Write the Raspbian image as before (CHECK TARGET DEVICE)
dd bs=1M if=2012-09-18-wheezy-raspbian.img  of=/dev/sde
6) If any partitions on the SD card auto-mount after writing unmount them using "umount"
7) Now boot your Pi with the SD card and it should work fine.