so dude. welcome to logic! it has amazing capabilities, but what it doesn't have is a dual g5 built in with 10,000rpm drives. i had all your problems. so i figured i'd throw another 2G into my setup with a dual g5, 2.0Ghz machine with 2 1/2 Gigs of RAM, two 7,200rpm drives, totalling over 300 gigs of space. i use logic pro7 and have a fresh OSX install, and i still get those errors. like david said to me while i was posting similar threads as you just did, "every machine has a limit."
the fact is though:
you don't make what you got with the best, its the other way around.
although:
you can start to learn tricks'
one very common and easy one is to freeze your tracks. it is the same as bouncing them down. but bouncing them down and then option clicking your instruments to shut them off is my trick. then i have that audio file to play with , and whatever changeups i made, but also i can go back and edit the instrument tracks just by turning them back on. its faster than freezing and unfreezing every few minutes. also you can sometimes take all your tracks with reverbs or delays and send them to just one bus with that effect. that works if you have similar settings on your reverbs, etc.
another thing is: if you're using like multiple battery instruments or what have you, just create one battery and load all those sounds and max it out. less is more.
the best s#!+ in the world was made with computers 25% as powerful as yours. just remember that.
but, yes, logic messes up for EVERYONE.
sorry, and good luck.
toiletooth
http://www.myspace.com/toiletooth