ChromeStar; that part is pretty normal. Depending on how memory intensive your scene is will determine how long it takes Poser to finish it's current calculation and clear memory. In other words: Put just a single prop in, use just default lights, set rendering for some Huge setting - start the render, hit cancel and it's very quick to stop. Then Load up the scene, say five La Femmes fully clothed. Now star the render and hit cancel. It will take some time to before it stops.

Currently I have one (several characters, lots of props, a few lights....it takes up to 15min to cancel out, then hangs again as I try to get back into preview screen. This is Not a P12 issue as my similar scenes are the same in P11, P10.....all way back to when Victoria and Mike first came out. Actually, I used to crash earlier versions trying to put too much in but since P11 I have been happy, no more crashing, just long hang times.