KSG

I know it's a late reply, but... Does the layer already have a mask? (It shouldn't, if you're just opening the game's dds files.) If not, try adding a mask, selecting "transfer layer alpha channel". Then you either alt+click or ctrl+click on the mask in the layers list to disable the mask. It is also an option in the right-click menu for the layer. When you're done, just use "apply layer mask" to turn it back into the layer's alpha channel. Weird workaround, I know. The channels tab (unless there's another one somewhere) only controls what you're currently editing, not what you're seeing. I do not know of any way to disable things, other than masks and entire layers.