automount doesn't work for Ntfs partitions on external Usb disks

Hi!
I'm running Kubuntu Feisty (7.04)
I have an external Usb disk, with two partition: the first one is fat32, the second one is ntfs.
When I plug it to my laptop, two windows popups, saying a new removable support has been plugged, asking what to do.
If I select the "Open in a new window" option, with the first window (about fat32 partition) everything is ok, the partition gets mounted and a new konqueror window appears; with the Ntfs partition instead, I can select any option, but nothing happens. The disk doesn't get mounted.
I tried to do it manually, I create a new dir under the /media folder, with the following permissions :
user (root): r/w
group (plugdev): read
other: -
but when I mount it manually, the dir changes its permissions and is accessible only by root user, using sudo or su.
When automount fails I find an error running dmesg:

"NTFS-fs error (device sda2): ntfs_lookup(): Found stale reference to inode 0xd18c (reference sequence number = 0x11, inode sequence number = 0x12), returning -EIO. Run chkdsk."

Does it mean something?
Any help would be appreciated. If needed I can post logs or other information, just ask me what is needed.
thank you! :)