Help with the type tool - please I am desperate

I try to type something in a psd but the text does not show. The text should have been black on white - so it is not the color. The marker that usually appears to mark where the text will be does not show either. The only thing I get is a small square dot. When I make a new layer and try to type in it the text typed does not appear in a new layer but in the previous type layer, so I am not able to make another layer with text.
What's interesting is that whatever I type I can see in the layers box, and actually the text is there, but I can not see it in the canvas.
If someone has any idea what could be the problem, please help me fix it...

Well if it is not the color. it must be the size.
Try to reset the type tool like this:
Goto "Window->character", click the character palette menu (the small right arrow) and then "Reset character"

Let us know the result
Good luck