I'm really not sure what changed. I purchased a licensed copy of Particle Fire 2 probably 6 months ago (or so). I downloaded a version of the screen saver to my machine (for the purpose of reinstalling in the future, if necesary), and installed it and it ran fine for the entire time.
Upon reinstalling on my new system, for whatever reason it stopped working, but you're absolutely correct, I downloaded the lastest version and the "Allow Multi-Monitor" option appeared in the Screen Mode settings and the screen saver immedaitely began to work on both montiors, at 1280x1024.
Thanks a million, I know it seems funny to be so excited about a screen saver, but it's not your average screen saver then either.