I have done all that you suggested again - with no changes.
I am sure I am missing something with the form builder in a fluid grid layout but going thru it again and changing all values to % did not make a difference to the form fields or the way thing stack when previewed.
I did re boot and cleared the cache as requested.
DW is still having trouble when a form is placed inside the fluid grid layout, very slow and catchy when you remover the form it all goes back to normal
There is no preview inside the form builder.