Then I think you want to do as my last post suggested and remove the $post[itrader_total] part:
PHP Code:
<if condition="$thread[forumid] == 45">
<a href="itrader.php?$session[sessionurl]u=$post[userid]"><img src="$stylevar[imgdir_button]/votar2.gif" alt="$vbphrase[votar]" border="0" /></a>
</if>
(You may have to play with the $thread[forumid] part. Sometimes you have to use $threadinfo[forumid] and sometimes you have to use $post[forumid] or $postinfo[forumid]. Sorry I can tell you exactly which one.)