I think you have nothing to worry about.
Check the image in different zoom %s and see if the black line disappears at high zoom.
If it does, it is just a screen artifact.
Incidentally, how is the image masked?
I have seen this sort of thing happen when clipping paths (PS) or clipping masks (AI) are used.
You might do better to use a layer mask in Photoshop (so the rest of the image is transparent in a psd file).
Then place the psd file.
This should definitely be o.k.
Reckon you must be just looking at a screen artifact.
You mean a tasty screen artifact, Steve?