[SOLVED] Can't access ext4 USB HDD

[pix3l]

dmesg is empty.. dmesg.0 is empty, too

df -h

Code:

root@xbian:/var/log# df -h
Dateisystem    Gr?sse Benutzt Verf. Verw% Eingeh?ngt auf
rootfs            30G    3,0G   27G   11% /
/dev/mmcblk0p2    30G    3,0G   27G   11% /
devtmpfs         188M    4,0K  188M    1% /dev
none              38M    468K   38M    2% /run
/dev/mmcblk0p1    34M     14M   21M   40% /boot
/dev/mmcblk0p2    30G    3,0G   27G   11% /home
/dev/mmcblk0p2    30G    3,0G   27G   11% /lib/modules
/dev/mmcblk0p2    30G    3,0G   27G   11% /xbmc-backup
/dev/sda1        917G    210G  661G   25% /media/gigastore

mount

Code:

root@xbian:/var/log# mount
/dev/mmcblk0p2 on / type btrfs (rw,relatime,compress=lzo,ssd,space_cache,autodefrag)
devtmpfs on /dev type devtmpfs (rw,relatime,size=191796k,nr_inodes=47949,mode=755)
none on /dev/pts type devpts (rw,nosuid,noexec,relatime,mode=600)
none on /proc type proc (rw,nosuid,nodev,noexec,relatime)
none on /sys type sysfs (rw,nosuid,nodev,noexec,relatime)
none on /run type tmpfs (rw,nosuid,nodev,noexec,noatime,size=38376k)
/dev/mmcblk0p1 on /boot type vfat (rw,relatime,fmask=0022,dmask=0022,codepage=437,iocharset=ascii,shortname=mixed,​errors=remount-ro)
/dev/mmcblk0p2 on /home type btrfs (rw,noatime,compress=lzo,ssd,space_cache,autodefrag)
/dev/mmcblk0p2 on /lib/modules type btrfs (rw,noatime,compress=lzo,ssd,space_cache,autodefrag)
/dev/mmcblk0p2 on /xbmc-backup type btrfs (rw,noatime,compress=lzo,ssd,space_cache,autodefrag)
/dev/sda1 on /media/gigastore type ext4 (rw,nodev,noexec,noatime,nodiratime,sync,data=ordered)

EDIT
xbmc.log --> http://pastebin.com/1U7BCrbP

I'm unable to navigate through the folders of that HDD. It says:
root@xbian:/media/gigastore# ls
ls: reading folders .: I/O-Error