L0XBY Booted up from my backup drive and started a full defrag of my main boot volume (60GB, 50% full, OS 10.5.6, journaled). About 20 minutes into defragging, iDefrag stalls and it shows the spinning beachball of death (I no longer hear the hdd reading/writing). Unable to shut down from Apple menu, I do a hard reboot by holding down the power button. I boot up from the backup drive again and start the full defrag of the main boot volume. This time it stalls after about 30 minutes of defragging, I get the spinning beachball and have to do a hard reboot again.
Full defrag runs fine on non-journaled volumes that don't have OS files on it. Maybe there's some incompatibility with OS 10.5.6? But it also stalled when I tried it on a 10.5.5 boot volume.
(Version 1.6.6)