You want to change the error message displayed? You will need to edit the template, find
Code:
<blockquote>
<p> </p>
<p><strong>This user has been banned.</strong></p>
<p class="smallfont">This member has been banned and their profile page is no longer accessible. Please check back once the ban has been lifted.</p>
<div> </div>
</blockquote>
and you will need to change the text 'This member has been banned and their profile page is no longer accessible. Please check back once the ban has been lifted.' to whatever you want it to say...