Yep, that's the same sort of issue I've had; you might try putting your alpha channel info into the transparency channel, as well, but I haven't had that help much.  Fortunately for this kind of mograph look, having that little light frame doesn't detract; in fact, it kind of feels like it should be there.  But it's maddening when you can't get it to work.  I'd suggest adding this to Daz's bug report.  Lack of full alpha accuracy can really screw up someone's day....

:D