Hi! I have the same problem.
If I upload the ArduinoOPCSample to MEGA 2560, it Works well and I can see into my MatrikonOPC Explorer (And the other examples…). But if I upload to Leonardo it Works at 50%
I can monitorize into “Serial Monitor” (pressing enter, and asking one of therse items –> “Easy testing of your OPC Sketch”), but in Matrikon I can connect to server but I cannot see the ítems.
NOTE: Windows 7 – 64bits.