DCOM errors typically begin with a "0x800" code. Specifically, the 0x800706BA DCOM error appears in the OPC Client application when the OPC Client "believes" that it has a live connection to the OPC Server, but truly does not. This can happen under several conditions. The OPC Training Institute’s website has a whitepaper that provides details on this error its various potential causes, and how to solve them using a step-by-step guide.