Theres a setting somewhere to dump the texture cache . I find it easier to save the scene , and restart Poser. Also check that you have lots of virtual memory available .

Look at your texture sizes too. I run most of the Daz stuff through a batch converter to  size them to 50% or even smaller . I then use those lower res images if its a background item .

you get a lot of 3000 x 3000 x 24 bit color images and memory goes fast.