When you say that synth playback seems jumpier, do you mean that:
a) the frame rate is lower (meaning, you appear to be missing frames of animation)
b) the frame rate is smooth but the actual path through the synth is more jerky
c) something else?
I loaded up your synth and it seems normal enough to me (actually a better reconstruction than one or two of your others I looked at last week) and it plays back as smoothly as any other synth for me.
If you have more programs open than you usually do (more tabs in the browser, more windows in general, large images open in an editor, etc.) then you may be running a little low on video RAM (assuming you are using Windows Vista or above, which would be using the GPU for the Desktop Window Manager) or if you have more synths open simultaneously than usual, it would cause synth playback performance to degrade until other things are closed which would give the Photosynth viewer more room to breathe on the GPU.