Try this:
http://www.pagerobot.com/pub/logout.zip
It contains the changed login.php script which ignores all new features and style changes.
Place the logout.php file in your forum home and call it (http://www.urforumname.us/forum/logout.php). If it works, it is definitively a style problem.
Template navbar - search for (about in the middle):
<td class="vbmenu_control"><a href="login.php?$session[sessionurl]do=logout&logouthash=$bbuserinfo[logouthash]" onclick="return log_out('$vbphrase[sure_you_want_to_log_out]')">$vbphrase[log_out]</a></td>
and replace with:
<td class="vbmenu_control"><a href="logout.php" onclick="return log_out('$vbphrase[sure_you_want_to_log_out]')">$vbphrase[log_out]</a></td>
Remember that sooner or later you will have to revert your styles, though :0
Special thanks to :
y2ksw