in vmmodel.php in line 657:
$limits[] = JHTML::_('select.option', '0', JText::_('all'));
may be need to replace 'all' in such way:
$limits[] = JHTML::_('select.option', '0', JText::_('JALL'));
?
good idea. But I doubt it works with j1.5 then, so I added COM_VIRTUEMART_ALL