You have tested other games and there are no issues with them?
If that is the case, you most likely have a driver issue. Maybe you need to roll back to a previous graphics driver. It is possible your graphics card chip manufacturer released a driver which causes heavy memory utilization in the game.
If that does not work, you then need to contact the developer of JC3 directly. They may have a work around or solution. They may also not even know of the problem and will need to know more info prior to fixing it.