I think I have the same problem as Jamo had.
I had an old 1004 20120508033925950 installation with a 500GB Sata disk partioned into / 100GB Swap 5Gb and rest for a data partition, the root user (or what it is called) was "linuxmce", filled up the disk with data and could use it well.
Later I bought a solid state disk, removed the old 500 GB disk, and installed again from the DVD, user this timed was "lmce".
a few weeks later I installed the and repartioned the 500 GB using gparted to only hold one data partition.
Booted up LinuxMCE, but LinuxMCE did not see the disk even after many(10 maybe) reboots and reloads, so I fired up X on the Headless installation, and there from dolphin I can see the disk, and when I try to access it I am being asked for a password and if I enter correct password for user "lmce" (note both user have different password) I can access the disk, but LinuxMCE still does not see it.
can this be same issue?