How many tracks with plugins are you playing back? Check the performance meter when playing back the tracks. When mine gets sluggish, the cpu meter is maxing out. Then I have to solo the tracks that are using Waves Rennaisance Comps one at a time, do a mixdown with no FX except compression, import the resulting wav file to an empty track, and delete the original. Rinse and repeat. Time consuming pain in the ass, but it frees up the cpu. Maybe a future update will have an easier way! 30 tracks with 6 or 7 Ren Comps WILL cause a serious log jam.