audio drop outs with instruments and FX

using cubase 7.0.2 on a imac 2.8 i7 12gb running osx 10.8.3

when changing sound presets i get audio drop outs. i get this problem using synths like retrologue and prologue
,pad shop ,and halion sonic se. at the moment i only now this with the synth i mentioned because these are the synth i use the most. this also happens when loading a effect into a insert slot. is the adio gard use to prevent audio drop outs in these situations.