Just a note in case your pulling your hair out. If you have a form that for all intents and purposes SHOULD be working but does not allow user input in a text field then perhaps this cold be your problem.
Try taking a look at the CSS on the element following the form. In my last encounter with this problem, it was a <p> that followed a form within a div.
The <p> had a CSS declaration of float:left and was inside a div that was floated to the right.