same problem.. forumdisplay threads aren't highlighted with new posts.. it still works for forums, just not threads.
peterska2 came up with this quick fix which should let you use vbplaza thread styles and still see new posts in the threads.
Code:
<a href="showthread.php?$session[sessionurl]t=$thread[threadid]$thread[highlight]" id="thread_title_$thread[realthreadid]"<if condition="$thread['titlestyle']">style="$thread[titlestyle]"</if>><if condition="$show['gotonewpost']"><strong>New: </strong></if>$thread[threadtitle]</a>
The result will be something like this:
New: unread thread title
New: unread thread title with style
read thread title
read thread title with style