it seems the new interface doesn't have a code syntax highlighter, and it does weird things to the code as well (like converting multiple tabs to "* " or something). I made my own highlighter, it's a PHP module with a function that takes the piece of code, the language and a line number bias as parameters, and colorcodes it accordingly. It can highlight C, C++, Delphi, Java, VB, VB.Net, C# and PHP code. It's written using C, C++ and flex.
You can try it here: http://www.oisyn.nl/tests/hl.php
Don't know how extendable vBulletin is, but maybe you can use it? It's open source btw.