InfoPath stores an allowable list corresponding to the assemblies located in the GAC (Global Assembly Cache) that have the Allow Partially Trust Callers Attribute (APTCA) set. An InfoPath form's business logic can only call into APTCA assemblies in the GAC which are on this allowable list. To add a new assembly to the allowable list, add a new String Value entry to the APTCA key. The Value Name field should be the public key token for the assembly and the Value Data field should be "1" for InfoPath to allow loading the assembly. If the Value Data field is not "1" the assembly will fail to load.