Over the last few days we've gotten numerous reports of problems with the Google Calendar API including failed logins, redirection issues, "Could not generate feed" errors, and the mysterious "Error=Unknown".
The problems are on Google's end and are not specific to Spanning Sync; if you sync Google Calendar with other applications or devices you'll notice that they're affected too.
We've reported the problems to Google and are optimistic that they'll be addressed soon. I'll update this post when we know more. In the mean time, the Google Calendar web UI seems to be unaffected.
Update: This morning (April 22) we got an update from Google on this issue: "A quick update—we see the problems you're having in our logs, it appears to be an issue on our side, it's not very widespread, we have some ideas why it may be happening, and we're thoroughly investigating."
Update 2: Trevor Johns at Google just posted this message to the Calendar API group:
"Google is aware of a problem with the Calendar Data API affecting a small subset of users. The affected users are able to access Google Calendar, but are seeing error messages when attempting to access API feeds.Update 3: Late last night we got word from Trevor at Google that they believe the problem has been solved. We'll continue to monitor our logs for signs of trouble. If you see any errors, please create a problem report (Advanced > Create report) and email it to us at email@example.com. Thanks!
We will provide an update by April 22, 2009 3:00:00 PM UTC-7 detailing when we expect to resolve the problem. Please note that this resolution time is an estimate and may change."