I installed Ubuntu 14.04 two days ago and I get the same error. But not always, I didn't understand why.
$ lsb_release -rd Description: Ubuntu 14.04 LTS Release: 14.04
$ df -h Filesystem Size Used Avail Use% Mounted on /dev/sdb1 9.5G 364M 8.7G 4% / none 4.0K 0 4.0K 0% /sys/fs/cgroup udev 1.8G 4.0K 1.8G 1% /dev tmpfs 371M 1.2M 369M 1% /run none 5.0M 0 5.0M 0% /run/lock none 1.9G 80K 1.9G 1% /run/shm none 100M 28K 100M 1% /run/user /dev/sdb11 151G 142M 144G 1% /home /dev/sdb7 19G 2.9G 15G 17% /usr /dev/sdb8 9.1G 667M 8.0G 8% /var /dev/sdb9 9.1G 22M 8.6G 1% /tmp /dev/sda2 233G 229G 4.4G 99% /media/marco/HD_ext_02
I installed Ubuntu 14.04 two days ago and I get the same error. But not always, I didn't understand why.
$ lsb_release -rd
Description: Ubuntu 14.04 LTS
Release: 14.04
$ df -h marco/HD_ ext_02
Filesystem Size Used Avail Use% Mounted on
/dev/sdb1 9.5G 364M 8.7G 4% /
none 4.0K 0 4.0K 0% /sys/fs/cgroup
udev 1.8G 4.0K 1.8G 1% /dev
tmpfs 371M 1.2M 369M 1% /run
none 5.0M 0 5.0M 0% /run/lock
none 1.9G 80K 1.9G 1% /run/shm
none 100M 28K 100M 1% /run/user
/dev/sdb11 151G 142M 144G 1% /home
/dev/sdb7 19G 2.9G 15G 17% /usr
/dev/sdb8 9.1G 667M 8.0G 8% /var
/dev/sdb9 9.1G 22M 8.6G 1% /tmp
/dev/sda2 233G 229G 4.4G 99% /media/