The solution we found was updating the Nvdia 4000 Card Control panel and the Driver and It helped.
Quadrotesla windows 7 Vers. 20097.3
Nvdia Quadro Transmit plug-in for CS6 to work with the mercury..
Now when we stop playback or stop scrubbing in the sequence the RAM will go down and will not keep on going up
Using the internal SATA disk was not the problem it always played smooth it only did problems when the memory when up to the maximun!