Webform Element Hidden by Webform Conditional Rule Still Tries to Validate

I have a section of a form with three Select Option controls displayed as list boxes. Of the three, only the first is mandatory.

The three controls are aligned horizontally inside of a Webform Layout Box. The Layout Box is displayed only if a Select Option displayed as a list box above it has the first option selected.

If options 2 or three in the previously mentioned Select Option are chosen, the above Layout Box is hidden. However, when a user clicks the submit button, the mandatory Select Option above, which is hidden from view, tries and fails to validate.

Has anyone seen anything like this before?

The site is Drupal 6, upgraded to the latest security release. All modules are up to date.

Thanks in advance.

Mark in SC_USA