Google currently has an issue with Docs service:
"We are currently experiencing a back-end outage that is causing higher than normal latency and error rates when using the Google Documents List API or the Google Spreadsheets API. The latency increase in some cases is 6 times that of normal. If you receive unexpected errors until this outage is resolved, I recommend retrying the request(s).
We're working to resolve the problem, and I will post back here when the issue is resolved."