Sub-category display differ; FF good, IE bad.

[SHK]

My site, sub-category page.

The category listing is wrapped in a div overflow, code below:

.centerColumn {
 height: 390px;
 Width: 830px;
 overflow: auto;
}

In Firefox, the sub-categories line up properly, 3 per row.
With IE, the lineup gets screwy.

Product listing, which is also wrapped with the same overflow
that gives scrollbars, is not affected.

What am I doing wrong?

Sincerly,
/Per