No idea - I was killing processes left and right, but with no result. The last thing I installed was
Live Mesh, but I had killed it during this problem.
My PC is freshly (more or less - September 18 in fact) installed (to put Windows 7 obviously), so there isn't much software installed. I do use Sysinternals utilities from time to time (mostly in my work PC though), but of course there wasn't anything running at that time. The only program I could think of that was remotely monitor-like was indeed procmon, but as you can see, it was not running. I probably
had started it during that session (I had closed it a long time ago), but again, why wasn't Movie Collector affected?
While writing these I thought of another experiment. I opened procmon, let it run for a while, and closed it. After closing it, I started Book Collector again. And lo and behold: The "Themis" message came up again! Again, Book Collector only, Movie Collector didn't even blink!
(Yes, it helps being a developer

)