Do you have write access to the calendar that contains the events want to modify? Does the error message is reported when pressing the buttons in the reminder dialog? The message seem related to handling of email based event invitations and not reminders.
(In reply to Stefan Sitter from comment #1) > Do you have write access to the calendar that contains the events want to > modify? I do not. > > Does the error message is reported when pressing the buttons in the reminder > dialog? Correct. The error happens when I try to press the "dismiss" button in the reminder pop-up - both "dismiss all" or "dismiss" the individual alert. I finally got the error to stop when I went to my calendar via zimbra, deleted it there, and then synced by calendar in Thunderbird. > The message seem related to handling of email based event invitations and > not reminders. Definitely could be for sure.
This explains it. You cannot modify events or reminders in a read-only calendar -> same as Bug 356002. Do you agree?
Ah - I think you're right. If I run into this error again and its' not with a read-only calendar/event, I'll reopen.