Thunderbird 9.0.1 Lightning 1.1.1 Windows XP SP 3 32-bit I have imported a large calendar (137 kb .ics file) with birthdays of people, some with alarms/reminders. Every time Lightning now reloads the calendar (why that often? remembering the next time an alarm will fire and check then should be enough), the alarm window/popup/alertbox shows a hang: A script on this page may be busy, or it may have stopped responding. You can stop the script now, or you can continue to see if the script will complete. Script: resource://gre/modules/XPCOMUtils.jsm:332 After saying Lightning it should continue, it often shows two more hangs, but the code file and line varies.

You can specify the reload interval in the calendar properties dialog. Otherwise probably identical to bug 362987.