Okay, You're an idiot.
By being a control freak, you've basically circumvented LinuxMCE's automatic measures. STOP THAT!
Let LinuxMCE partition itself appropriately, and this problem won't happen.
Under LinuxMCE's default, there is a single partition for everything. If you want more space than what is on your disk, either:
(1) Plug in a NAS brick to your network, let LMCE manage it, whammo, instant storage.
(2) format a disk as linux, and plug it in as SATA/eSATA, USB, or Firewire. LinuxMCE will ask if it can use it as storage.
(3) use the web admin to group a series of disks as a RAID.
Pick one of those three.
Do NOT manually symlink or manipulate mounts, you will break the system.
STOP THINKING LIKE A LINUX USER! THIS IS AN APPLIANCE.