Header Image Issue

[CivilWarTalk]

I just visited a customer who happens to be using IE7, and when they visited my site, my header image was hidden behind the forum, almost like there is some bad CSS settings. This left an odd looking space above the forum where the image should have been, but I can't figure out if this is an actual error in my style that newer browsers are auto-correcting, or if this is just a flaw in IE7. In IE8 the header looks fine.

I know IE7 is not the most popular, but I would like my forum to look good in as many browsers as possible. Can anyone tell what needs to be corrected to fix this?

My Site: http://CivilWarTalk.com