Custom workflow fails as auth workflow but succeeds as action workflow

Hi all,

I'm building an environment that contains a couple of custom object types - one of which holds details about applications, and the other which contains a request to install a given instance of one of these apps.

Some of the applications are subject to one or two levels of authorisation, with custom escalations and thresholds, so I'm trying to make it as generic and extensible as possible by holding these as attributes on the application object.

So for now, I'm simply firing an approval to the first approver by initially looking up the "ApplicationInstallRequest" for the corresponding application, and then from the latter object reading the approver.

This works as an action workflow, but as an authorization workflow I receive an "access denied" error at the first read resource activity, with:

Error processing your request: The operation was rejected because of access control policies.
Reason: The server workflow rejected the operation.
Attributes:
Correlation Id: df7f8849-3921-48e9-ba75-14ad6298fa79
Request Id: 623c0d79-5594-4ebe-b562-480a4c750959
Details: Microsoft.ResourceManagement.WebServices.Exceptions.PermissionDeniedException: ResourceIsMissing at Microsoft.ResourceManagement.WebServices.RequestDispatcher.ExecuteGetAction(RequestType request) at Microsoft.ResourceManagement.WebServices.RequestDispatcher.ExecuteAction(RequestType request) at Microsoft.ResourceManagement.WebServices.RequestDispatcher.ExecuteAction[ResponseBodyType](RequestType request) at Microsoft.ResourceManagement.WebServices.RequestDispatcher.DispatchRequest[ResponseBodyType](RequestType request, Guid requestIdentifier, Object redispatchSingleInstanceKey, Boolean isRedispatch) at Microsoft.ResourceManagement.WebServices.RequestDispatcher.DispatchRequest[ResponseBodyType](RequestType request) at Microsoft.ResourceManagement.Workflow.Hosting.RequestWorkItemProcessor.DispatchRequest[TResponseType](RequestType request, Boolean applyAuthorizationPolicy) at Microsoft.ResourceManagement.Workflow.Hosting.RequestWorkItemProcessor.ProcessGetWorkItem(ReadRequestWorkItem readWorkItem) at Microsoft.ResourceManagement.Workflow.Hosting.RequestWorkItemProcessor.ProcessWorkItem(WorkItem workItem).

Do I need to specify the resource from the currentRequestActivity, or am I missing something else?

Thanks,

Paul