The Terms of Service on the cart is not being validated before the user goes to the checkout. (Virtuemart 2.0.20b, Joomla 2.5.9)
The fix is to add the following views/cart/tmpl/default.php (after line 61)
$document->addScriptDeclaration (”
	jQuery(document).ready(function($) {
		$(‘a.vm-button-correct’).click(function(event)
			{
				if( $(‘input#tosAccepted’).is(‘:checked’) )
				{
					document.checkoutForm.submit();
				}
				else
				{
					$(‘a.terms-of-service’).css(‘background-color’, ‘red’);
				}
			});
		});
	“);
