The fix ended up being banning the ASP tag altogether.

Users will still be able to post ASP code in the code tag.

As you're going to need the fix for your board...

In ubb_lib, find this:
<pre> push (@returnarray, "PHP") if (($this =~ m/<?php/si) &#0124;&#0124; ($this =~ m/&lt;?php/si));</pre>

And replace it with this:
<pre> push (@returnarray, "PHP") if (($this =~ m/<?php/si) &#0124;&#0124; ($this =~ m/&lt;?php/si));
push (@returnarray, "ASP") if (($this =~ m/<%/si) &#0124;&#0124; ($this =~ m/&lt;%/si));</pre>

There are also new protections against the short tag formats...