I followed the instructions on your page step by step. I even had to create the behaviors folder, as there wasn't one included with the default files with r58.
This bugs me. In your installation of C2 R58 you didn't had a folder "behaviors" in "C2_basefolder\exporters\html5", you had to create it ?
If so, you couldn't use 8direction, bullet, scrollto behaviors and others.
If you still had access to those, then you copied the pathfinder in the wrong place.
I'd suggest you to uninstall C2 and install r59 at any rate then.
Just out of curiosity. I notice this was a caproj file. Do you have it on a capx? I have had no issues with capx files yet. (knock on wood)
The link I provide in the PathFinder topic is to PFDemo.capx, not caproj.
Anyway, a .capx is a compressed .caproj (project folder). (You can open .capx files in 7zip for example)
Install R59 and follow the steps again.
Make sure the pathfinder files are in "C2\exporters\html5\behaviors\pathfinder" and then open the capx.
It should work.