Open includes/functions/html_output.php (do not forget to backup first!)
a) find(1.3.6 line 267):
if (strtolower(IMAGE_USE_CSS_BUTTONS) == 'yes' && strlen($alt)<30) return zenCssButton($image, $alt, 'submit', $sec_class /*, $parameters = ''*/ );
replace by:
// bof css buttons (submit)
if (css_button_allowed($image) === TRUE) return css_button($image, $alt, 'submit', $parameters);
// eof css buttons
b) find (1.3.6 line 293 before edits):
if (strtolower(IMAGE_USE_CSS_BUTTONS) == 'yes') return zenCssButton($image, $alt, 'button', $sec_class, $parameters = '');
replace by:
// bof css buttons (button)
if (css_button_allowed($image) === TRUE) return css_button($image, $alt, 'button', $parameters);
// eof css buttons