I was having this same issue, and found a solution.

1) Log into calendars.office.microsoft.com
2) Click on my office online
3) Under subscription services on the left, click outlook calendar sharing
4) Click on delete calendar profile (this only erases all shared calendars,
it doesnt do anyhting to your live ID)

5) after this you need to go into outlook, click tools, account settings,
published calendars and then change account, follow the instructions, next
next next and then finish
6) You can then click publish my calendar in outlook
7) I only get one shot at inviting people, so make sure you enter all email
addresses this first time

Hope this helps!

"Helen" wrote:

Sam problem - I have already shared (restricted sharing) my calendar onine -
but have been trying to add another person all week and get this same error
message - did anyone solve it??

Many thanks


"Jeff Cashman" wrote:

I set up a shared calendar on office online with the publish feature in
outlook2007. I sent the initial invite during the setup and it worked fine.
Now I am trying to add additional users with the right-click Share Calender
and it creates the email fine. I add receipents and click send and get the
following error: error while preparing to send sharing message. server
returned an error.

It's driving me nuts