Connection Error every time i plugin my reader (PRS 350)

Hello,

i am new here and my first post is a question.

I use Calibre 0.8.61 with Ubuntu 12.04 erverthing works fine until now. Last time i pluged in my Sony PRS 350 and Ubuntu and Calibre had found the reader and a nautilus window of the reader poped up. I closed the window to work again with Calibre. Few seconds later there was a Error warning of Calibre. Now every time i open Calibre and plugin the reader, Calibre find the reader but ew seconds later following Error pops up.

calibre, version 0.8.61
FEHLER: Fehler: Fehler bei der Kommunikation mit dem Gerät

[Errno 30] Das Dateisystem ist nur lesbar: '/media/READER/database/cache/media.xml'

Traceback (most recent call last):
File "/usr/lib/calibre/calibre/gui2/device.py", line 82, in run
self.result = self.func(*self.args, **self.kwargs)
File "/usr/lib/calibre/calibre/gui2/device.py", line 339, in _books
mainlist = self.device.books(oncard=None, end_session=False)
File "/usr/lib/calibre/calibre/devices/prs505/driver.py", line 199, in books
bl = USBMS.books(self, oncard=oncard, end_session=end_session)
File "/usr/lib/calibre/calibre/devices/usbms/driver.py", line 246, in books
self.sync_booklists((bl, None, None))
File "/usr/lib/calibre/calibre/devices/prs505/driver.py", line 228, in sync_booklists
c.write()
File "/usr/lib/calibre/calibre/devices/prs505/sony_cache.py", line 727, in write
with open(path, 'wb') as f:
IOError: [Errno 30] Das Dateisystem ist nur lesbar: '/media/READER/database/cache/media.xml'

The reader seems to be ok because when i use the original Sony software everthing seems to be ok.

Can sombody help me? I want to use Calibre again. Sorry about my bad english.

Stefan