With the introduction of the August Cumulative Update for SharePoint 2007 (KB973399) we encountered “System.NullReferenceException: Object reference not set to an instance of an object.” on all pages inheriting from MySitePublicWebPartPage.

I have a clean install on the latest and greatest: Windows Server 2008, SQL Server 2008 and MOSS 2007 SP1 with all updates. Everything works fine, except the search crawl gave Access Denied errors on http://mysite and sps3://mysite. This post explains how I fixed the problem.