Left-menu column appears anywhere on the screen using IE6

I had the same problem, but only on a small screen with large fonts. Resizing the browser window demonstrates the problem; as the window gets smaller, the left sidebar moves across the center column toward the right. Commenting out the additional rule limiting the container width to 70% helped somewhat. Finally, I eliminated the right sidebar and now the left column stays in its place until the browser is resized to less than half the screen width. I'll call that a "win" for my purposes.