I think you may have missed the point in my reply:
Form Toolkit _IS_ compatible with DW CS5.5
CSS Form Builder _Version 1.x_ _ IS Not_ compatible with DW CS 5.5. Version 2.x of CSS Form Builder _IS_ compatible
in other words:
you can use from Toolkit in DW CS5.5
but you cannot use CSS Form Builder version 1.x in DW CS5.5