Grid container width doesn't resize to parent?

Suite and Optimus Suite 5
#1

I know this must be something silly and simple, but I can’t figure out what. My grid container looks like this:

I initialize the grid like this:
var grid;
grid = new dhtmlXGridObject(‘container’);
// set up the column headers and various column properties…
grid.init();
// load the data…

I have a css style on the container that looks like this:
div #container {
width: 100%;
height:300px;
}

But my width css declaration is always overridden by a computed width that shows up in the style attribute of the rendered container div. (Usually something like 1265.2px). I need the grid’s container to resize with its parent. Is there an attribute I’m not setting? Any ideas where I should look?

Thanks!