Live 6 Multiple VST midi track problem

[nykx17]

I've been having this problem where I have multiple midi tracks (12-15+) with different plug ins some of the tracks will just stop playing or making any noise. As of now i use 3 vst synths Absynth, fm8 and massive. I'd like to add more plug ins and be able to have atleast 20 some odd tracks 80 percent of which are midi vsts. I run this all on my mac book pro with two 2.66 duo core and 3 gigs of ram. So i cant imagine its the comp anythoughts?