White Edge / Halo around Alpha Maps.

Hey, for a long time I've been having an issue with opacity not displaying correctly, i.e. it showing off a white edge to things. Is there a way to fix this?

I've used TGA files.

^ This is what the alpha map looks like. It works perfectly with the diffuse but I'm not sure why when importing it into SP it has those edges. The issue also appeared when importing things back into SP after I've exported from SP (and they looked fine when I exported them).