Viewing Synth on Photosynth site. In overhead view. Then clicking on a highlight thumbnail causes IE8 to stop working. I could reproduce the stop under same conditions.
I could reproduce it here, too. Seems to be a serious bug that has been overlooked till now.
It indeeds looks like a bug, I will file a bug in our bug database and we will fix it in an upcoming release, thanks for taking the time to report this.
Synthing means a whole new photo experience to me. I enjoy it a lot. Sure I like it to get better and better until it can celebrate its final release. Happy to have been able to make a useful contribution.