Your fast reply is much appreciated, thank you. I will try to reinstall the USB to Serial drivers and change the COM port nuber by using different USB ports.
You are right, Vrsim application works fine, is just LINDA who's failing to take control of MCP v.II and I suspect that although the right port appears in green in LINDA settings as well as in Fsuuipc ini file, the port is not really un use.
LISA works fine w/ FSX, when I click "reload LUA" I even get a notiffication on FSX.
Regards
C.