We run into this once in a while. What we tend to find is that some element of the page is overlaying the fields in the form. Try going to edit the landing page, then click once to select the form. Then access the "Property Sheet" and change the value in the layer. The default is 15, and we usually change it to 50. Editting that will bring the layer that the form sits on and therefore will hopefully bring it above the element that is blocking the click events.
Brennan McAdams