Just wanted to say many thanks for this solution; I found it wasn't really necessary to use Firebug or zmmailbox however.
I did a dump of the ICS and also found around 9 million "\n"s in a particular entry. I made a note of the DTSTAMP: number, found the item in the calendar owner's web interface by date, (in my case DTSTAMP:20080423T085906Z = 23rd April 08) and simply deleted it from there. Everything's been fine in Lightning since.
Maybe I'm missing something important but it seemed easier this way. Obviously no easier to do 100 calendars tho... |