Right column appears below content on left side on homepage only

This problem occurs when viewing the initial home page using both Firefox 2.0.0.8 and IE 7.

I am using Zen Fixed. The problem occurs with both 5.x-0.7 and today's 5.x-1.x-dev versions.

The right column appears beneath the left column. The top of the right column is horizontally in line with the bottom of the content area.

The problem only occurs on the initial homepage. The homepage content area consists of the latest SimpleNews post, followed by some static content.

The width of the content area does not appear to be wider than when viewing any other page.

Any help would be greatly appreciated.

Thanks.