So, a few times I've suddenly had my G5 Power Mac, running Leopard, suddenly become very slow. Each time I opened Activity Monitor and got a surprise: iCal was for some reason chewing up 2GB+ of RAM. This has happened about half a dozen times over a couple of months. Not a huge problem, force quitting it and relaunching it makes things all rosy again, but it's a curious problem, and I've never had it on any other Mac of mine. Googling hasn't turned up anything. A while ago I also had a problem with iCal beachballing for a few seconds every half dozen or so operations, but that hasn't happened for a month or so. iCal is the only app I've ever had either of these problems with, I've got a pretty vanilla OS X installation, and apart from these intermittent memory leaks things are running along buttery smooth.