Might be a bit late at this point, but I wonder if this is a sandbox issue. Does photoFXLab work when it's double-clicked upon? It may need to be enabled to run in Gatekeeper. Quit Aperture if it's open, then right-click on the photoFX application and launch it with "Open". From there you can enable it to be opened, then quit and see if it'll run in Aperture.
I tried what you said. I didn't see an option to "enable it to be opened". It just opened.
No difference in the Aperture behaviour. When I try to use PhotoFXLab, I get the message that Aperture is preparing the photo (presumably converting it to TIFF), photoFXLab opens and then the normal photoFXLab screen but blank where the photo should be.