I ran into the same problem with the same template. It took me a few minutes to find the offending line, but once isolated, I inserted the line (referenced below) per Muffin Man's instructions -bingo. . . back to normal! ;D I'm curious like Nickza -does anyone know why this happened? In my case I'm running this template on 1.5 RC3, but in legacy mode. Could that be the issue?
error_reporting(0);
if ($color_index && isset($tab_colors[($tab_index)%count($tab_colors)])) {
$id .= $tab_colors[($tab_index)%count($tab_colors)];
$tab_index++;