File store sometimes fails

[green3g]

I randomly get these request failures in my logfiles:

Traceback (most recent call last):
  File "c:\python27\lib\site-packages\wfastcgi.py", line 826, in main
    result = handler(record.params, response.start)
  File "c:\python27\lib\site-packages\flask\app.py", line 1997, in __call__
    return self.wsgi_app(environ, start_response)
  File ".\flask_app.py", line 16, in __call__
    return self.app(environ, start_response)
  File "c:\python27\lib\site-packages\flask\app.py", line 1978, in wsgi_app
    ctx.push()
  File "c:\python27\lib\site-packages\flask\ctx.py", line 332, in push
    self.session = self.app.open_session(self.request)
  File "c:\python27\lib\site-packages\flask\app.py", line 912, in open_session
    return self.session_interface.open_session(self, request)
  File "C:\www\flask_app\virtualenv\lib\site-packages\flask_kvsession\__init__.py", line 160, in open_session
    current_app.kvsession_store.get(sid_s)
EOFError

Any ideas?