OK, I have a solution for syncing events with alarms created on the N900 back to the Mac, and I need a couple of volunteers to test it for me.

WARING! WARNING!
This solution involves changing one of the system libraries on your N900 (specifically /usr//lib/libcalendar-backend) as such I will not be providing instructions on how to do this, if you are not completely comfortable with .deb files, this isn't for you. This may brick your device, it may prevent you from installing PR1.2, it may damage all your data on both your N900 and your Mac. In fact, assume it will so any loss is your fault, not mine.

That said, if you want to help, send me an e-mail at dave at smithfamily.org.uk absolving me of all responsibility for the well being of your data and hardware, and I'll send the update out.

Just to reinforce the point, this is nothing to do with Nokia, it is not sanctioned by them, and it may well break things. This is purely a request for help in testing something and will not be final version. If any of this makes you feel uneasy, don't volunteer and hope my fix makes it into a future official update.