Careful. vBulletin is XHTML 1.0 Transitional. That means your tags have to be xhtml, not html. Specifically, this means they should be lowercase: <div></div>.
Also, while Transitional allows "align=center" as an attibute, XHTML Strict does not. So it would be good practice to start using CSS for all styling.
Code:
<div style="text-align:center;"></div>
For your purposes, try "float" instead of align:
Code:
<div style="float:left;">My left content</div>
<div style="float:right;">My right content</div>
It's also good practice not to bump threads with off-topic posts. The OP asked about centering, so likely no one will look at this thread for a solution to left/right alignment.