Comment 3 for bug 369737

This is happening to me, I found this bug in the PEAR mediawiki filter. the code from there is:
<?php
function parse()
    {
        error_log("parser called");
        $this->wiki->source = preg_replace_callback(
            $this->regex,
            array(&$this, 'process'),
            $this->wiki->source
        );
        error_log("Returning parse");
    }
?>

Potential things to look at: the regex is getting confused? I'm also using macrons in my content.