If I may make a note here, I had the same problem when I decided to give GameGuru a try, I have used FPSC for many years,
and right out of the box. I had all kinds of issues with GameGuru with Entity's not displaying etc..
I went in and even used my Take Ownership right clicky as It had to be a permission issue, I use Win7 64bit. To get everything to work I went to the GameGuru directory and changed Administrator to Everybody, and changed permissions to FULL Control.
Since doing that everything works fine.
I am not sure. But the theory is some times the security settings go with the file and messes things up.