EXS 24 Logic Sampler Users Group

Help, I've got this great pianist in my and studio there's a slight lag 
between when he hits the keys and when the notes are heard. I'm using a midi 
keyboard thru mt4 on a G5 1,8 single Mac into Logic 6.4.3 - playing The Old 
Lady Post piano in exs24...I thought there was a quick fix in the audio 
hardware window in an earlier version of logic platinum. I checked the 
manual but sofar to no avail...

Please guys  - let me know a fix; this should be easy; am I losing my mind? 
what have i overlooked?...my brain is melting...

Thanx,
Micke Nilsson