meeting organizers don't see my acceptance

I am having an issue with Calendar 7.0 on OSX 10.9.2.

When Wintel users send a .ics meeting invitation to my email account, I can doubleclick the attachment, which opens in Calendar with all the correct details, and "accept" the meeting. My status shows with a green check as "accepted" here in Calendar. But the meeting organizer doesn't get a response from me. Is there something I need to do in my preferences to enable others to see my status correctly?

Thanks.