Euch. Kindle connection problems...

[Clio1837]

Hi guys! I've been having a problem, and I hope someone here can help me... I've been using Calibre with my Kindle 2 for a few months now, and everything has been fine. But today, I suddenly started getting error messages. Specifically, I get "Error Communicating with Device" messages. The details are these:
[Error 2] The system cannot find the file specified: u'F:\\'

Traceback (most recent call last):
File "site-packages\calibre\gui2\device.py", line 81, in run
File "site-packages\calibre\gui2\device.py", line 332, in _books
File "site-packages\calibre\devices\kindle\driver.py", line 202, in books
File "site-packages\calibre\devices\usbms\driver.py", line 242, in books
File "site-packages\calibre\devices\usbms\driver.py", line 375, in sync_booklists
File "os.py", line 157, in makedirs
WindowsError: [Error 2] The system cannot find the file specified: u'F:\\'

if that helps someone smarter than me;-) So far, I have turned both Kindle and computer off and on again. I've updated to the most recent version of Calibre. My Kindle is charging fine, so I don't think it's the cable. I have changed the USB port that I was using, and no difference. Any ideas? Thanks a lot!