In the moreneat theme the center column was appearing all the way to the right and at the same size of the the other two columns leaving most of the center blank. This was tested in IE6 and IE7. It worked fine in FF. I made a slight change to the CSS and then tested it in all three browsers and it seems to work.
Here is the diff for docs/templates/styles/moreneat/tiki.tpl:
51c51 < <tr><td id="tiki-columns" colspan="0" width="100%"> --- > <tr><td id="tiki-columns" colspan="0" width="auto">