Obviously the template of the email configuration dialog is broken.
<br />
Please update installation with current opengroupware-webui packages or 
update your sources and rebuild OGo.
<br /><br />
The quick fix, if you see this exception:
<pre>
   cd ~opengroupware
   find . -name "LSWMailPreferences.html"
</pre>

   and replace ":/#font" with ":&lt;/#font&gt;", the "&lt;" is missing.
<p>
Some other template has such syntax errors aswell (we cleaned up a lot of 
templates prior to OGo checkin, so some might contain errors).<br />
What did you click on? Please report to the users mailing list. 
</p>