EXS 24 Logic Sampler Users Group

I'm nw to EXS24, I loaded my drum samples and they play back but with 
delay. They are sometimes too fast or too slow. How do I get rid of 
this latency problem? I have a Dual 1.8 GHZ Apple Mac G5 running 
Logic 6 pro.I only have 512 Ram.
Please help me set this up well.Its the only one I can use for my 
drum samples.
Thanks
Steve