This typically happens if you have a custom style that has the pop-up menu html contained in the template named "navbar" To fix this I usually have to open the DTO Garage navbar template and cut out some code and paste that code into the vBulletin navbar template for that style. Below is an example of what that might look like:
Original DTO Garage Navbar template
PHP Code:
<td class="vbmenu_control"><a id="navbar_garage" href="dto_garage_help.php$session[sessionurl_q]" rel="nofollow">Garage</a> <script type="text/javascript"> vbmenu_register("navbar_garage"); </script>
<div class="vbmenu_popup" id="navbar_garage_menu" style="display:none">
<table cellpadding="4" cellspacing="1" border="0">
<tr>
<td class="thead" align="left">Garage</td>
</tr>
<tr><td class="vbmenu_option" align="left"><a href="$vboptions[bburl]/dto_garage.php$session[sessionurl_q]?do=index">Garages</a></td></tr>
$dto_garage_plus_search
<tr><td class="vbmenu_option" align="left"><a target="_help" href="$vboptions[bburl]/dto_garage_help.php$session[sessionurl_q]">Help</a></td></tr>
</table>
</div>
</td>
New DTO Garage Navbar template
PHP Code:
<td class="vbmenu_control"><a id="navbar_garage" href="dto_garage_help.php$session[sessionurl_q]" rel="nofollow">Garage</a> <script type="text/javascript"> vbmenu_register("navbar_garage"); </script>
</td>
New addition to vBulletin Navbar template
PHP Code:
<if condition="$show['popups']">
<div class="vbmenu_popup" id="navbar_garage_menu" style="display:none">
<table cellpadding="4" cellspacing="1" border="0">
<tr>
<td class="thead" align="left">Garage</td>
</tr>
<tr><td class="vbmenu_option" align="left"><a href="$vboptions[bburl]/dto_garage.php$session[sessionurl_q]?do=index">Garages</a></td></tr>
$dto_garage_plus_search
<tr><td class="vbmenu_option" align="left"><a target="_help" href="$vboptions[bburl]/dto_garage_help.php$session[sessionurl_q]">Help</a></td></tr>
</table>
</div>
.
.
.
Again your mileage may vary as all skins are done a little differently. For example in one site we integrated Garage Plus into we had to change the DTO Garage Navbar template from being enclosed in <td> tags to <li> tags while also moving the pop-up menu code to the vBulletin navbar.
Hope this helps!
Mark