Error communicating with device (Kindle)

[reedg_01]

Any ideas?:

[Errno 22] invalid mode ('wb') or filename: u'D:
metadata.calibre'

Traceback (most recent call last): File "site-packages\calibre\gui2\device.py", line 64, in run

File "site-packages\calibre\devices\kindle\driver.py", line 177, in books

File "site-packages\calibre\devices\usbms\driver.py", line 164, in books

File "site-packages\calibre\devices\usbms\driver.py", line 305, in sync_booklists

File "site-packages\calibre\devices\usbms\driver.py", line 303, in write_prefix

IOError: [Errno22] invalid mode ('wb') or filename: u'D:
metadata.calibre'

Thanks