In my experience (P5 sr4.1 pc firefly render) I can only cancel if Poser is actualy in the final "render" stage where it is putting the image on the screen. If its adding objects, or rendering shadow maps, yould better wait or your going to lock it up. Onece it gets to the final stage you can kill it "safely". At least it has always worked for me (occationaly it will take a minute, but it will cancel out)

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