Javascript regex replace weird behavior

I'm developing a js to dig up Bible references on Portuguese web pages, and link them to a youversion.com url.

This is one of those pages: http://www.adventistas.org.pt/Evangelismo/Web/Img/Downloads/Trimensario/2012/1t/online/licao7.htm

This is the script: http://www.adventistas.org.pt/Evangelismo/Web/Img/Downloads/Trimensario/2012/1t/online/bibleref.js

It pretty much works, but it acts kinda funny, and can't find out why.

Sometimes it outputs empty links with correct bible references, and then outputs the real link, with a wrong reference.

Eg:

<a target="_blank" href="http://www.youversion.com/bible/verse/arc/gen/2/1-3" class="passagem"></a>

<a target="_blank" href="http://www.youversion.com/bible/verse/arc/gen/2/1-3" class="passagem"></a>

<a target="_blank" href="http://www.youversion.com/bible/verse/arc/gen/2/1-3" class="passagem"></a>

<a target="_blank" href="http://www.youversion.com/bible/verse/arc/gen/2/1-3" class="passagem"></a>

<a target="_blank" href="http://www.youversion.com/bible/verse/arc/gen/2/1" class="passagem">Génesis 2:1</a>-3;

Sometimes it works perfectly. Can anyone help track down the culprit?

Thanks!