This is probably an issue with the page that you are adding a form to. Mismatched html or a missing body tag. If you attach a copy of the page I can try to reproduce the problem and help you use the wizard properly.
Your friends over here at WebAssist! These Dreamweaver extensions will assist you in building unlimited, custom websites.
These out-of-the-box solutions provide you proven, tested applications that can be up and running now. Build a store, a gallery, or a web-based email solution.