From the number displayed on your page I'd say you didn't add the $stime to the "global..." line. I don't have neither 5.5 nor 5.5.1 installed so what I've told you above is from one of my scripts and the instructions/line numbers are from looking inside ubbt.inc.php. I used ubbt.inc.php from 5.5.1 as reference so this may explain why yours is slightly different. Regardless of that, if you change 'global $config, $theme, $thispath, $VERSION, $ubbt_lang, $timea;' to 'global $config, $theme, $thispath, $VERSION, $ubbt_lang, $timea, $stime;' it should work.
