Update: Further reading has linked the freeze possibly to Mac users who are running Unsanity’s Application Enhancer. I had it running with a dock modifier, a lot of folks use it for “shape shifter.” The recommendation, if you are ahead of the curve and haven’t gone the hard way already, is to uninstall App Enhancer before you upgrade to Leopard. Here is a link to their support page for uninstalling: http://unsanity.com/support.php?vf=15.

This is good news to Apple fans who can potentially chalk another failure up to third party software and not directly to Apple.