It seems that if you are returning from a linked workflow back up to the originating workflow, you had better be sure that the originating workflow was started within the context of a NavigationGraph (not as open navigation). Starting the originating Workflow as openNavigation means having a blank originatingNavGraph value and that seems to kill the TaskArgs on the way back up to it from the Child workflow

Problem If using OpenNavigator, add default=”true” to StatePersistence declaration in config file Resolution Server Error in '/Dev/UIPABWeb' Application. Object reference not set to an instance of an object. Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. Exception Details: System.NullReferenceException: Object reference not set to an instance...

Resolution If using OpenNavigator add default=”true” to state declaration in config file Problem Server Error in '/Dev/UIPABWeb' Application. The state object for the navigation graph is not configured. Check the /configuration/uipConfigura... node in the application config file (AssemblyFileName.config or web.config). Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about...

Resolution If using OpenNavigator, add default=”true” to ViewManager you want to use Problem Server Error in '/Dev/UIPABWeb' Application. Object reference not set to an instance of an object. Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. Exception Details: System.NullReferenceException: Object reference not set to an instance of an object.Source...

Resolution State element was referencing wrong assembly in object types, and nav was using wrong name anyways (to reference state provider) Problem Server Error in '/Dev/UIPABWeb' Application. The state persistence provider for the navigation graph UserAdminNavGraph is not configured. Check the /configuration/uipConfigura... node in the application config file (AssemblyFileName.config or web.config). Description: An unhandled exception occurred during the execution...

Resolution Another config error, the line describing this had the version where the assembly name was supposed to be Problem Server Error in '/Dev/UIPABWeb' Application. Configuration Error Description: An error occurred during the processing of a configuration file required to service this request. Please review the specific error details below and modify your configuration file appropriately. Parser Error Message: The IViewManager Microsoft.ApplicationBlocks... cannot...

Resolution section name="uipConfiguration" type="Microsoft.Application... /> The version number and public key token on the assembly were out of synch Problem Server Error in '/Dev/UIPABWeb' Application. Configuration Error Description: An error occurred during the processing of a configuration file required to service this request. Please review the specific error...