Thanks inmazevo for that in depth test session... Did Apple support give you anything? Surely they cant ignore that post??!!
I'm having exact same problems on Macbook pro 2.16 core duo, 2gb ram and Logic 8 using both internal audio and an RME FF400 (not at the same time of course) and have tried so many different things I am close to giving up on Logic 8.. sad really.
Did anyone get any further with this?
Thanks,
esb