Often the texture maps are large which eats your memory for breakfast.  Since I'm not zooming into skin pores for most of my renders, I tend to batch resize them.  Half or Third Size of a 4000x4000 set of textures does wonders.

Good free tool for that here: http://www.rw-designer.com/picture-resize

Allows a lot of extra command line parameters if you are extemely picky, like me.

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