I am using OSX 10.6.2 and CS4. I have both tried editing a form that I had, as well when creating one from using the any from the built-in templates in FB. I tried just doing one without any template as well, but got errors when it tries to preview the form in FB.
I have tried to create forms in php from the insert-webassist-CSS FB as well straight from the Webassist dock.
Do you know if this might have issues due to other extensions I have installed?
When you're creating a form, does this error occur for all forms you have created or just a specific one? If its a specific form, what steps are you taking to design the form?