I've been experiencing this problem for some time as well, and I finally found a solution. In your Layers display, click the problem text layer, then go to Layers; Layer Style; Blending Options. On the bottom of the Blending Options dialogue box is a "Blend If" section. There are two gradient bars: "This Layer" and "Underlying Layer." Each bar has a dark slider on the left, and a light slider on the right. On the "Underlying Layers" bar, move the dark slider all the way to the left, and you should see your text fill in nicely. Hope that helps.