Server Explorer and the DSC Engine are independent of each other.
The only reason that I can think of for having a problem where only one of the two can connect to the OPC Server at the time is that the OPC Server itself is limited to one connection only.
Make sure that you are communicating directly to the OPC Server from both DSC and Server explorer and that you are not trying to connect to the OPC Server from Server Explorer through DSC.
Regards,
VG