Some months ago I was sent an appt by email for inclusion in iCal. This happens frequently - normally without a problem. On this occasion however it was rejected:
"calendar can't accept the event [name of event]....etc"
"The account [name of account] currently can’t be modified. To discard your changes and continue using the version of your calendars that’s on the server, click Revert to Server".
However despite clicking Revert to Server many many times I keep getting the message every time I have iCal open.
Retrieving data ...