access right with OPC Client run as a windows serv

Question

I write a OPC client process in MFC, and everything is OK when I run it directly in VS2010. But when I install it as a windows services, problem comes. I still can connect to OPC Server, but after connected I check the status of the OPCServer with IOPCServer::GetStatus(), and it returns false! Is there something I need to watch out when I install the process as a windwos service?Or some settings of the OS need to set? (My OS is Win7)