Looks good to me in both FF 3 and IE 7
I can see an small issue in both FF3 and IE7, at the lower right corner where the content meets the footer.
That is the 1.3 version you are using. If I remember correctly, I ran into issues with that version concerning page children display as well. I think that was last updated for WP version 2.3. The i3Theme Version 1.3 also contained some workarounds for a known “no sidebar” issue.
Updated versions can be found here. Might be worth a try before you get too involved in modifications. Version 1.7 (centered and right), both worked fine for me on WP 2.6. Maybe just upgrading the theme would get you in the right direction.
Good luck!
Looks fine in FF here — the footer image (rounded corners) needs to be some 20px longer to cover the main div.