I've been struggling with this problem for a long time and perhaps there's someone here that had the same issue and managed to solve it.
When rendering alpha sequences - whether it's PNG, Targa or Tiff - I get a ca 1-2 pixel white line around the whole object.
I usually working with motion tracked footage so the lines becomes quite present when composing the CGI sequences with the film footage.
Been trying various settings with AA, Image sampler and Color mapping but nothing seems to solve it.
I'm composing in After Effects with Premultiplied Alpha and render in 3D studio Max.
What I usually do is to add a matte effect to the layer and remove the white line; which also removes some of the shadows that I would like to remain.