Mount missing partitions in Ubuntu 11.10

I found that one of my partition in windows was missing in Ubuntu, so I tried to mount it back. Firstly type:

$ sudo fdisk -l

to check what are partitions available. And I figured out that sda4 is the partition missing, so I tried

$ sudo mkdir /media/e
$ sudo mount -t ntfs -o nls=utf8,umask=0222 /dev/sda4 /media/e

But it gave me:

Mount is denied because the NTFS volume is already exclusively opened.
The volume may be already mounted, or another software may use it which
could be identified for example by the help of the 'fuser' command.

Maybe it’s because auto-mount performed by Ubuntu somehow grab the handle, so I unmounted this partition first and mounted it back by:

$ sudo umount -l /dev/sda4
$ sudo mount -t ntfs -o nls=utf8,umask=0222 /dev/sda4 /media/e