Several things come to mind.
1. There's a layer on top of the text that is blocking it. Try moving the text layer to the very top of the layer stack and see if it shows up.
2. There's a blend mode on that's affecting it. At the top of the layers palette make sure the blend mode is set to normal.
3. The opacity is set to 0% or near there. Make sure the opacity of the layer is at or near 100%.
4. You are using the type mask tool to create the text. Right click on the type tool in the tool box and make sure you are using the correct type tool.
Hope this helps. I'll check back later to see how you make out.