Apologies for the delay, - my presets have all gone loopy - driving me nuts.
Finished version (test site) is here, and the zipped files are here..
Another version (a by product) is here, with the zipped files here.
You will still have to make the forms' action direct to your form-processor.
Check out the validation functionality, it works fine for me.
After all that, it seems that if the form action field (to anything other than blank, or the page the form is on), is completed during the form builder process the FormBuilder will not create server-side validation code. If you leave it blank or add the page the form is on, the server-side code is created.
I'm guessing you had the formmail cgi script entered in the 'action' page field during this process?
Anyway, see how the linked to forms work out for you,