Hi Malcom - Just so you know - the "improper argument" thing started when VSD released a new version around the same time as new versions of IE and Firefox came out. With new browsers come new glitches

Other people have also had some text issues since then. The 'problem' with VSD is that it produces fairly clean and compliant (for a WYSIWYG) code, code that will validate. Most WYSIWYG programs produce a real mish-mash of code soup to make them as fool-proof as possible. With VSD, I've found it's probably best to keep things simple - not a lot of overlapped items and special effects - and preview in all the major browsers before an upload.
With the improper argument warning, I've been able to get rid of it by pressing the Esc key several times. The site is just as it was before the warning, nothing lost and I can pick up where I left off.
Web Form Builder is being re-worked. Sometime soon Coffee Cup will be releasing the new non-Flash Form Builder. All HTML/CSS so it will be usable on any device/computer and compliant with modern browsers.
Keep in mind, no WYSIWYG is perfect, and every time major updates come out (whether to the program or web browsers), there will be hurdles to overcome.