This tip was just posted on another blog i read.
If you are creating multiple text layers in a document sometimes when you click in your photo with the text tool it will just put the curser into a previous text layer and not create a new one. If this happens just hold the shift key down when you click in your photo area and a new layer will be created.
Another way to do this is to duplicate one of your text layers and then double click on it in the layers palette to alter it. It will all highlight and you can start it over from scratch.