AHA! That's definitely one possibility, since I was syncing it. And you're right, it was funky now that I think about it. Birthdays was the only 'other' calendar my N900 would put into a separate category, which made some sense. But then it also made a 'normal' entry for birthdays as well (ie: a person's birthday would show up twice on that day -- once in 'Birthdays' green, once in 'Normal' blue)

To put it mildly My girlfriend and I both use the same iCal 'account', just with different colours (6 plus the Birthdays calendar) to distinguish between our various activities, so there is a LOT of information in there.

I think that's exactly what happened.

I'm not sure if it's the same for everyone else, but my N900 has been using blue to represent all the events it's brought in via sync. This is also the colour of the calendar I have selected in the iSync preference "Sync all events created on the phone to.."

Somehow I guess iSync decided all the events in the N900's calendar had been created on the phone because suddenly I had a duplicate blue event for every event in iCal.. even the blue ones, which was odd.

Luckily I've got three Macs and a .Mac subscription, so I was able to revert to a 'clean' copy without too much fuss. Accordingly, I'm quite happy to do any testing you think might help you sort this out

In the meantime, I'm pretty content just moving my data one-way. The plug-in is still a massive lifesaver even with the odd quirk.