I have exactly the same problem. Nvidia with ubuntu 12.04. With two monitors attached and unity running, compiz consumes 50% of CPU, and computer becomes unusable. I am able to solve the problem by either (i) removing one of the monitors or (ii) disabling the unity plugin; just as the original reporter stated. I am running the latest nvidia drivers available through jockey.
I have exactly the same problem. Nvidia with ubuntu 12.04. With two monitors attached and unity running, compiz consumes 50% of CPU, and computer becomes unusable. I am able to solve the problem by either (i) removing one of the monitors or (ii) disabling the unity plugin; just as the original reporter stated. I am running the latest nvidia drivers available through jockey.