I'm new to MacMusic so hello all!

I just upgraded to a 24inch imac, 2.66Ghz - 4gb ram. I am running logic 8 with a fireface 400. Everything is great apart from when I have a fair few tracks running (eg 12 audio and 12 software) the response time from clicking and dragging a fader or knob is really slow. I have to wait a few seconds for it to catch up with itself. This seems strange as there is no CPU overloading. I have checked activity monitor whilst logic is playing and there is loads of room, (70% of CPU remaining + over 2Gb of ram spare).

It is also a bit slow when copying and pasting parts of tracks.

I have the Audio driver Buffer set to 256 although changing this makes little or no difference. Also I have Universal Track mode on, Software monitoring on, Large Process Buffer Range.

Also my fireface is up to date.

I am baffled and would really appreciate some help!