Image won't render with Adv Raytrace Shadows?

[AFK_Matrix]

I am trying to render a still out at 2000x1500 with a direct light and sky light. I have Adv Ray Trace Shadows on and when I click render I get a message saying there is not enough memory for the Raytrace Generator and it can't do the shadows. This happens both on my work machine and the render machine. Whats weird is in all the other images I have ever done I have Adv Raytrace on and have had no problems. All the settings are the same across all my stills and I have just rendered 10 other stills with the same setting with no problems. I also tried doing a restart on my machine, had just Max open and the task manager open, its only using 600mb of memory, and I have 3gb available?? I also bought the model into another drawing where the Adv Raytrace works still now luck

 

 

EDIT: Forgot to say if i switch to normal Raytrace Shadows it will render.

Very puzzled.