For a long time, I've had google.com as a service authorized to access my Calendar: http://imgur.com/8eAX6.png
Clicking the "revoke access" link returns the expected message http://imgur.com/jKdX2.png

Unfortunately, google.com always comes back as an authorized service few minutes later. Do you know which Google service requires this authorized access, and why I can't revoke the authorization? Does any one else have this issue?

I've deleted all my calendars and tasks, disabled all labs features and no mobile device are set up with Calendar (neither SMS reminders nor ActiveSync).

Thanks for your help.

Try iGoogle Calendar Gadget

Done, no tab/gadget on iGoogle.

Should I understand that the service "google.com – Calendar" is really a Google services, or could another website pretend to be "google.com"? Should I understand that it's only my Google Calendar that requires this connection, or could it be someone else's Google account having access to my Calendar data? And would my Google Calendar be the only data accessible via this authorization?

Thanks for your help

Here's a related thread in the official Google Apps Help Forum http://www.google.com/support/forum/p/Google+Apps/thread?tid=44a4a8e6fbcf1656, with no answer/comment so far.