Ads not centered

[killa101]

Hey all. I was wondering if you could help me to get my google ads centered in my header. Here is how they are positioned right now:

http://www.pb-addict.com

You will notice they are aligned to the left but I want them centered.

Here is the code that I am using.

<if condition="$show['guest']">
<!-- Sponsor Ads -->
  <br /><table class="tborder" cellpadding="$stylevar[cellpadding]" cellspacing="$stylevar[cellspacing]" border="0" width="728" align="center">
  <tr>
  <td class="tcat" colspan="6"><phrase 1="$vboptions[bbtitle]">Sponsors</phrase></td>
  </tr>
  <tr>
  <td bgcolor="#000000" colspan="6">
  <div align="center">
  <script type="text/javascript"><!--
google_ad_client = "removed";
google_ad_width = 728;
google_ad_height = 90;
google_ad_format = "728x90_as";
google_ad_type = "text_image";
//2006-11-01: removed
google_ad_channel = "9295759247";
google_color_border = "000000";
google_color_bg = "000000";
google_color_link = "ffffff";
google_color_text = "ffffff";
google_color_url = "ff9400";
//--></script>
<script type="text/javascript"
  src="http://pagead2.googlesyndication.com/pagead/show_ads.js">
</script>
  </div>
  </td>
  </tr>
  </table>
  <br /><br />
  <!-- Sponsor Ads Ends -->
</if>

note: i just upgraded from 3.5.4 and that was the code i used in 3.5.4 and it worked then.

I just realized, this only happens in FireFox. In Internet Explorer its fine.. Any ideas what is wrong here?