Unrelated to ACP 6. The PierTech dome driver was set to "" for the COM port, then when it was called to connect, it returned Conversion from string "" to type 'Integer' is not valid. (the port number presumably) and failed. The error coming from the Dome driver was so unspecific it was hard to tell. Plus, it's odd that the driver lost its COM port setting. I looked at it in the ASCOM Profile Explorer and found that it's not saving its settings there. So I don't know enough to even suggest how to avoid the problem. He's going to talk to PierTech.