I had to roll back an update which was causing trouble, and rever to FIM version 4.1.3510.0.

Things look ok, but workflows with custom activities are ending in PostProcessingError, and I see this in the event log:

"Forefront Identity Management Service is not able to serialize this XOML definition"

Checking further in the event log, I see

"System.Workflow.ComponentModel: System.Workflow.ComponentModel.Serialization.WorkflowMarkupSerializationException: Could not load file or assembly 'Microsoft.IdentityManagement.WFExtensionInterfaces, Version=4.1.3510.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies."

However, if I check in C:\Windows\Assembly, that DLL is actually there, with the proper version.

Any hints?

Thanks in advance,
Paolo

Also, in the config file (C:\Program Files\Microsoft Forefront Identity Manager\2010\Service\Microsoft.ResourceManagement.Service.exe.config), I have this binding redirection:

      <dependentAssembly>
        <assemblyIdentity name="Microsoft.IdentityManagement.WFExtensionInterfaces" publicKeyToken="31bf3856ad364e35" culture="neutral" />
        <bindingRedirect oldVersion="4.0.0.0-4.65535.65535.65535" newVersion="4.1.3510.0" />
      </dependentAssembly>

Nevermind, I brilliantly solved the problem by Restarting The Service (tm).

90% of MS issues are resolved by a Restart.  the other 10, never mind.