After having to revert my graphics drivers because the latest AMD drivers refused to see my second monitor, the original THQ PSEditor stopped working, just errored and quit.
So I went back to the Steam version and, although the application loads up okay, nothing in the editor worked. I discovered what directory it was HARD CODED TO LOAD AND SAVE FROM (really?? a file picker in Windows is so easy to implement, this is outrageous. If I had made this I would have been fired).
So
@lixiss used the word "permission". And I thought "permissions"? So I "ran as administrator" and the Steam version actually worked! WTF?? I have to run PSEditor as administrator? WHY??
So I could work with and see the emitters and grid lines, great. The background color no longer saves to the pseditor.cfg file like with the original THQ version, guess that was also too much trouble to port over to the new versions. Oh well.
Anyway, I wanted to post this in case someone ends up from a google search in the future. Along with the other helpful tips in this thread, try running PSEditor as administrator and see if that does the trick.