Instead of opening another topic I am going to post here as I have the same problem.
Just installed 14.4 the latests snap shot and ran a sudo update.
Plugged in my USB 4TB Seagate Expansion Desk external hard drive with all my media, and the LMCE didn't ask to added it to the system.
Instead I had to mount it to /home/public/date/videos/dvd (dvd is a new folder I created )
sudo mount /dev/sdb2 /home/public/data/videos/dvds
The drive works prefect in 10.4 and LMCE picks the device up with out any issues.
As you can see from the out put of lsblk, the device is there
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sda 8:0 0 465.8G 0 disk
|-sda1 8:1 0 461.9G 0 part /
|-sda2 8:2 0 1K 0 part
`-sda5 8:5 0 3.9G 0 part [SWAP]sdb 8:16 0 3.7T 0 disk
|-sdb1 8:17 0 128M 0 part
`-sdb2 8:18 0 3.7T 0 part /home/public/data/videos/dvds
sr0 11:0 1 1024M 0 rom
Here's a link to paste bin with the out put of my system specshttp://pastebin.com/EZGrwY7v