To start, make sure that the local Administrator account has been added to the DCOM security permissions lists, and that the System account has been added to the permissions list on the PC with LabVIEW. If the error persists after the DCOM settings have been verified, LabVIEW may be running under a different Windows user account than the one under which it was installed. To resolve the issue, try re-installing LabVIEW under the user account on which the LabVIEW OPC client project will run. This will allow the OPC components of LabVIEW to run as that user, so that the error will no longer be posted. LabVIEW should not need to be uninstalled first.