KOrganizer error: std.ics - AkonadiTray

[joneall]

All of a sudden, every time I modify an alarm on a calendar item in KOrganizer, I get a couple of popups with the message

std.ics - AkonadiTray
Unknown error. (There is no trasaction in progress.)

What in the world is this? Should I worry? How do I get it to stop?

Thanks in advance.