I found that this problem occurred when I had a filename with Cyrillic characters in one of my other add-on scenery directories (so the path was invalid). When I fixed this, the objectflow crash stopped and I could load the sim.
This directory was set in an add-on.xml. Even when this other add-on was disabled in Prepar3d (ie, active=false in the add-on.cfg), objectflow still crashed the simulator at the splash screen.
Bryn.