All forms on Webvanta sites include, by default, a "honeypot" field that is hidden by CSS. If this field is filled in, then it is very likely that the submitter is a spambot (we get thousands of such submissions every day).
However, some form-filling utilities, including that built in to Chrome, are filling in this field and inadvertently triggering the spambot blocker.
To prevent this, we are now including the attribute autocomplete="off" in all of our form elements. This keeps Chrome and presumably other form-filling utilities from being blocked from submitting forms. It does have the side effect of preventing use of the auto-form-fill feature on forms on Webvanta sites.
If it is important to you to have auto-form-fill on your forms, you should remove this attribute, as well as the honeypot field (contact us for details). This will, however, increase the amount of spam you receive via your forms.