I’m able to reproduce the freeze and I believe the plug-in is trying to perform actions that require user input which isn’t possible when the modal “Preparing Plug-ins for First Use” dialog has focus. Using the plug-in manager or drag/drop to install works fine, because this dialog isn’t shown. This is related to the plug-in loading for the first time during Rhino startup, rather than a specific installation method.
@dale do you have any pointers here? Is is possible for a plug-in to show UI when the “Preparing Plug-ins for First Use” modal dialog is open? On load, the plug-in attempts to minimise Rhino in order to bring its own dialog to the front. I also see the
-Open command being called, but again the command line is unable to receive input. Either one of these situations will prevent Rhino from starting.