Ok. If you say you can type onto the image but your text comes out small at 72pt this is probably because you have the resolution of the image set to high. Unless you are using the image to be printed the resolution should be about 72dpi. You should also save you image as a PSD file before editing it and then save for web. Create a new layer for text and make sure you don't have a strange font selected.
Hope this helps.
roryt
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I think roryt is on the right track.
Look under image and tell us the resolution and size.
hughv
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