I just got a monster of a mac pro and i am having the same problem you guys have in 10.5, so i was glad i still saved the previous version of logic. However, the clean install i did with the previous version also has it’s problems, mainly giving me the spinning ball and not reacting when saving or quiting a project sometimes. I know a lot of you like to update stuff , but on my old mac i had the most stable os and logic i ever had. I never updated the os, and i advise you to turn off all automatic updates and think first. Whenever u hit a stable combination of software/hardware, clone it as a steady point to return to