Detecting log-ins with SENS

I have a .Net service that uses SENS to detect when a user logs on or off. I'm having two problems, though:

1. Even though the service seems to be starting automatically, if there is only one user on the computer and that user doesn't have a password (meaning windows will start right away), the log-in doesn't seem to be getting detected. Is it possible that the service is getting started too late? If so, what are 开发者_如何学运维my options?
2. I don't seem to have a way to detect windows switches users. In other words, if I log in with person A, I can detect that. If I then switch users (meaning person A doesn't log out) to person B, person B logs in and I detect that. But if I switch back to person A, no log-on has taken place, and I don't know that the switch took place. Is there a way, via SENS, to catch these events. I seem to only be able to catch Display locks/unlocks, logging on/off, when the screensaver starts/stops, and when the shell starts. Is it possible to do more with SENS, or perhaps to detect when the user is switched using these operations? Or perhaps by some other technique?

ISensLogon2 gave me SessionDisconnect and SessionReconnect, which happen when the user is switched without logging off. I don't have a technical way to solve the second problem, so I'm just circumventing it.