You're in luck, I've been bored this morning.
Try increasing the height of #wrapheader to equal the height of your sitelogo + the margin on the .sitelogo container. I think that would be 161px.
That should do the trick but if it doesn't try explicitly stating your relatively positioned containers as relative. IE7 has some issues with relative positioning when the containers aren't explicitly relative.
If neither of those work, just keep tinkering with it. The CSS you included in your post doesn't appear to be anything that would help.
Do you know about the IE Developer Tools? While using IE8, just press F12 on your keyboard and a screen will appear. They don't work as well as FireBug but at least you can select different elements and see how they are positioned.