kittiewan: sorry for the delayed answer.
I've looked into your capx, and indeed, I believe the PF can't handle to be run several times each frame, it sounds like too much calculation.
For the part about enemies spawning in the top corner, it has to see with the event to make the enemies move (based on Yann's formula).
Apparently it results in getting a X, Y to 0, and that's why the enemies keep staying in the top of the screen.
I've looked (not that deep) into it, and I guess the formula should be adapted to your project, but I haven't dug much. (you can see it by toggle disable said events, the enemies won't move, but will be spawnt in the "starting rectangle".)
A solution if you really want to use the PF is to "delay" the number of times it gets executed each second (instead of each second, execute it every 10 ticks or so), this could allow the soft to run a bit smoother (no promises there though, it's theory <img src="smileys/smiley17.gif" border="0" align="middle" />).
Mercy is probably right though, the PF might not be the best behavior to use for "chasing ghosts" type.