Wondering if this problem happens if you are trying to share your calendar
with someone that you had already sent an invite to earlier. I encountered
the same problem - I was trying to share my calendar with someone who I had
already attempted to share it with some time ago, but had forgotten that I
had sent out an invite to share my calendar. So when I was trying to send out
this invite it kept giving me this error.

After some digging around I found that if I right clicked on the calendar I
wanted to share, and went to "publish to the internetchange sharing
permissions" it gave me a list of people who were "sharing" my calendar. I
clicked on the name that I wanted to resend the invite to and removed that
name from the list. After that when I tried to resend the invite it worked
without a problem.

Hope this helps!

"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