Comment 20 for bug 564459

I had this issue also. In my case, there was a glitch at some point during a fresh installation. Even though the root drive on my laptop /dev/sdaX was where / and swap were set up, the fstab file listed the / partition as mounted on /dev/sdb1. i have no idea how the system managed to boot with this incorrect configuration. the fix for me was to use "sudo blkid" to get the UUID of the / partition and then used that to correct the fstab file to mount the correct partition (/dev/sda1) to /.

i discovered this when trying to mount a flash drive (which was detected) using gnome's Disk Utility from the System|Administration menu. I had an error when trying to mount the flash drive partition from there that said there was a helper failure claiming /dev/sda1 was already mounted at /.