Mounts causing "hiccup

I decided to start a new project to play around with the 1.5.3 Mac beta. Unfortunately I ran into a bit of odd behavior with mounting objects. For some reason every time an object is mounted the scene freezes for a split second. I took the same script and ran it under 1.1.3 and the hiccup does not exist there. Anyone else run into this or could I have something setup wrong that is causing the issue? Thank you.