@perpetualrevision - thanks for your reply. From your description it is not clear if this a problem with Poser or some kind of resource leak or in driver/library issue but I don't know enough about how Macs work to know where to look. Regarding posing multiple horse/riders - in the past I just used one rider/horse but setup the different poses as animation key frames. Once all the poses had been setup the figure was duplicated and I used the pose dots to copy the key frame to frame one. This also had the benefit of being able use the animation interpolation to create additional poses if there are many horse/riders to setup - the process probably works best when the figures are very similar.