Best I can tell, by looking at the Maya help file, (always useful when you hit a brick wall) :headbang: is that the filmTranslate attribute is looking for TWO numbers . . .

From Help file :

filmTranslate (ct) double2 0.0, 0.0
Post projection translation component. Translate the film back by the given values.
The values are normalized with respect to viewing area.

filmTranslateH (fth) double 0.0
Translate in horizontal direction.

filmTranslateV (ftv) double 0.0
Translate in vertical direction.

So evidently it needs you to either supply it with two numbers,
and I'm not so sure how to do that without a little more research that I am to lazy to do, or break it down to :

zoom_camShape.filmTranslateH = pan640x480.translateX;
zoom_camShape.filmTranslateV = pan640x480.translateY;