Adding FX creates playback noises

whenever I add FX like ReaVerb, the playback has ticking noises. when I render the tracks though, it's not there.

your audio card buffer size is too small, or you should disable synchronous buffering in your reaper settings, or your cpu can't keep up.

playback noise 

Thanks! I am using a Dell D620 Dual Core so I dont think it's a CPU issue. I am guessing I can change the sound cards buffer size somewhere. thanks again