Start by reducing the size of your images to no more than 2500 x 1750. It will make for a much snappier editing experience, reduce the load on your system and still allow for some mild pan and zoom.
That was it Harm. I thought for some reason since it was a static image the size wasn't as important but I made them 2500 and it's working fine now. Thanks.
Actually, we see the Still Image as just that, a "still" Image, but PrPro sees it as Video, when that Still Image is on the Timeline. That is why, when you drag it to the Timeline, there is a red line above it. For ultimate playback, one will want to Render at least that part of the Timeline.
PrPro, as of CS 5, can handle larger Still Images, and can also Scale those Images very well, through MPE (Mercury Playback Engine) - better than previous methods to Scale internally.
However, when there are "extra pixels," those still pose greater overhead on the computer, as all the extra pixels do have to be processed too.
I am still a bit "old-school," but will calculate the movement that I will need, and Scale to the exact pixel x pixel size, to eliminate any "unused pixels," to keep the overhead to a minimum.
Good luck, and if one does need to work with large Still Images, to alllow for Motion>Position Keyframing, or similar, then Rendering the Clip, that is now formed from those Still Images, will get the best possible playback.