Issue with expressions in ITSM Web Client under NT Authentication

Error: (when using the standard web client)
Error executing rule:Business Object: ProblemField: KnownErrorDurationError executing rule Known Error Duration:Business Object: ProblemField: KnownErrorDurationObject type cannot be converted to target type.
or
Error executing rule:Business Object: ProblemField: IncidentCountError executing rule Problem Incident Count:Business Object: ProblemField: IncidentCountObject type cannot be converted to target type.

Version:
ITSM Version 504SP patch level 3 (081106) applied
Using SQL 2000 Database

Summary
The error seems to be related to any expression that is executed on a field on any object. This error occurs when trying to save the affected business object. Similar errors occur in the Self Service interface. Error occurs only when using the NT Authentication pass through.

Solution
The Solution to the error seems to be applying Patch3a (082506) to the system.

Have applied this to the site that was having the issue, restarted IIS and the users are now able to create Problem records without the error, via NT authentication.

Note: all web.config files (etc.) are overwritten as part of the patch process