I have two other sites on the same host running SVN192 pro (all sites with the same Joomla! version) and I used the same browser. The other sites did not suffer the hang up on initializing.
After reading other posts in the support forum suggesting script or browser issues, I emptied the browser cache. This solved the problem! (I assume the browser was using a cached script from the previous version).
My recommendation is to clear out browser cache when upgrading versions.