If you can see the "channels" you should be able to fix the areas you need to. I know if Photoshop you can.

It's not really that tga doesn't hold an alpha...it does. And so does png. It's just that Poser has a hard time having all that in one file ;). I always go in and make a black and white from the channel. ;). Most of the time they're flipped opposite anyway and are white where they should be black and vice versa.

The preview in Poser is going to show areas of a mask as a color..even if it's transparent in reality and technically there's nothing there. Even if it looks sorta messy, if you look at the image on the main node, you're still getting trans where you should be ;).

Laurie