MOSS Site Usage report error (and crash)

This happened today;

The symptom of the problem is that when trying to access the site usage reporting in MOSS the user (who does have access) is prompted to authenticate, upon failing to authenticate the worker process falls over.

The app event reports the following error: .NET Runtime version 2.0.50727.42 - Fatal Execution Engine Error

The SSP1 & Portal application pools both stopped running.

The resolution is the application of a non-public hotfix to ASP.net 2.0: http://support.microsoft.com/kb/913384