Few of the group members might have faced problems, in last few hours, while accessing their Groups Calendar from Groups site and would have run to following error message
"Your access to this calendar is being processed. Please check back later."
We are really sorry for the inconvenience caused to you due this. Good news is that the issue has been fixed.
Meanwhile, in future for any reason you if you run into any issue (hopefully never) while accessing your Groups Calendar from your Group site, you can try accessing it from calendar.yahoo.com and there is a good chance that its working fine there.
Thanks again for your patience while our team worked through this issue.
Y! Groups and Calendar Team