Alternative to overflow:auto (sidebar without tables)

Hello,

I am currently making a vBulletin skin, and was wondering if there were any alternative to overflow: auto? The thing is, I'm trying to create a sidebar without tables AND with a fluid wrapper.

My CSS code looks like this:
[CODE]
#wrapper {
width: 90%;
min-width: 980px;
margin: 10px auto 0 auto;
background: #1a1a1a url(images/magnetic/style/wrapper.png) repeat-x top left;
border: 1px solid #161616;
overflow-x: hidden;
-moz-border-radius: 8px 8px 8px 8px;
-webkit-border-bottom-left-radius: 8px;
-webkit-border-bottom-right-radius: 8px;
-webkit-border-top-left-radius: 8px;
-webkit-border-top-right-radius: 8px;
}

#right-content {
float: right;
width: 275px;
color: #7a7a7a;
padding: 15px 0;
}

#left-content {
margin: 0px 0 0 0;
background: #e9ecee url(images/magnetic/style/bg-main.gif);
padding: 0px;
min-height: 800px;
overflow: auto;
overflow-x: hidden;
-moz-border-radius: 8px 8px 8px 8px;
-webkit-border-bottom-left-radius: 8px;
-webkit-border-bottom-right-radius: 8px;
-webkit-border-top-left-radius: 8px;
-webkit-border-top-right-radius: 8px;
}[/CODE]

And here's what the HTML looks like:
[CODE]

Right content (sidebar) here

The left content here

[/CODE]

The thing is, when the overflow:auto is there, the page looks fine BUT it has issues when opening, for example, dropdown menu or expanding a big image.

Here's what it does when opening a dropdown menu:
[img]http://www.skinbox.net/community/uploads/images/skinbox-1274211421-U1.jpg[/img]

Here's what it does when trying to open an image:
[img]http://img689.imageshack.us/img689/936/magnetic740x340problem.gif[/img]

So what I'm trying to do, is to create a fluid layout with a right sidebar without tables. It's working, although I'm looking for some code modifications so it doesn't have issues with the dropdowns etc. Basically, it seems that everything looks fine BUT when we open something that is "larger" than the #left-content ID. Then it creates issues.

Floating both elements (left-content and right-content) will not work. Well it will, but when you reach a certain resolution, everything will mess up. Here's a screenshot of the 2 elements being floated (left content floated to left and sidebar floated to right) with a resolution of 1280x1024. Floating both elements is useful for fixed layouts only.
[img]http://www.skinbox.net/community/uploads/images/skinbox-1274278039-U1.jpg[/img]

Any idea?

Thank you so much in advance.