Thanks for replying.
It's possible that I did save the sim while it was running. I guess, when doing this, it will then be running when I perform future restarts? Unless I save it again, paused, in which case future restarts will not start it runnng?
I'll try to get in the habit of always pausing, restarting, and saving (with it not running). This is usually what I intend anyway, since I always want to save a simulation in it's original (time = 0.0) state. Sometimes, I forget, though, and it seems there's no way for me to get the simulation back to it's original (time = 0) state, unless I load a previously saved simulation. I guess I have to think of the saving procedure as it works with most games... saving it at a certain point in time. As I'm using US as a research tool, I guess I'm considering to be saving the sim as it was at time=0, and expect it to always be loaded at time = 0 and paused.