I don't know if this would make a difference, but your callbacks aren't returning anything and they are defined as :Int() in the API declarations. I'm almost positive it's something related to the way the callbacks are declared, because you're not passing anything to the library other than the -1 in PhidgetOpen().
Unfortunatly I don't think there is anyone where who's used that particular piece of hardware.
Unfortunatly I don't think there is anyone where who's used that particular piece of hardware.