[SOLVED] External Harddrive mounts itself read-only

[pix3l]

Hi,

Software
XBian version: XBian v1.0B2
XBMC version: default
Overclock settings: default

Hardware
Power supply rating: > 1Amp
RPi model (model A/B 256mb/512mb): B 512MB
SD card size and make/type: 32GB Class 10
Network (wireless or LAN): wireless
Connected devices (TV, USB, network storage, etc.): WiFi and USB HDD

Logile
Link to logfile(s): http://pastebin.com/rbbxcBqN

Problem description:

I have a strange Problem since a couple of weeks:
My XBian boots normaly and recognizes my external HDD without problems. But when I start to transfer files onto my external HDD, after the first 5 or 6 files I get an Error that says:

Code:

Writing failed: The filesystem is only readable

The only way to gain access again is to reboot the complete system.
Doing a "umount /media/gigastore" work, but I can't remount the HDD
When I do "mount /media/gigastore" it says

Code:

mount: can't find /media/gigastore/ in /etc/fstab or /etc/mtab

As far as I know I did not change anything besides doing updates with
apt-get update && apt-get upgrade

Any ideas?