I am using:

Joomla 1.5.17
Community Builder 1.2 (with no modifications)
ARI YUI Menu 1.0.4 (for this example but I get the same result with any drop-down menu)
URL timeshareownerscommunity.com/exchange-rent/userslist.html

It really would help me to have a drop-down menu on top of this userlist but it seems like all of them go under, I know it is not a problem with the menus (I have tried several) because they work fine anywhere else.
Thank you for your time and valuable help.

Hi. It could just be me, but I dont think I understand exactly what your concern is. Assuming we've never seen or used your site before (because we haven't) please be as clear as possible on exactly what you are talking about.

I cant see any drop down menu under the userlist

Exactly that it's the problem, you can't see the drop-down menu because it goes under where the "User-List" starts.
The menu item "America" has 2 sub-categories"E.U." and "Mexico", E.U. has plenty of sub-categories but you can't see them because the "drop-down" goes under the list.
This happens with any menu that "drops-down" to the space occupied by the "Userlist".

Thank you for your time and help ckayfish.

The content that is on top when you use the drop down is in a div called "rt-block"

The module you have for you menu is yuimenubar, and uses a combo of inline and CSS styles. There are even some z-indexes being defined.

In a quick look I couldnt tell exactly how to resolve. I suggest using somthing like Firebug and start inpecting the CSS and look into how you could set the z-index of various "parts" to layer things properly.

Anyway, the conflict looks like its with Gantry/rockettheme (your template) and the menu module. Nothing to do with CB from what I can see.

Thank you ckayfish!
I will look in to the template.