I am running Retrospect under the same ID as I am logged in as and I have Admin rights. So I don't think Vista's issues with multiple ID's apply in my case. My second point is that Retrospect is a single instance program in that when you disable the activity monitor and launch Retropsect you get a dialog box that says another instance is running and click on 'OK' to kill it and start up Retrospect. Your solution only kills the current session and restarts the program. I need to gain entry into the currect session so I can address issues such needing additional media, etc.
Currently, I am starting the program and letting it stay up and running so when the backups start I can see the media usage, but that is a work around and not a solution.