First off love the theme, it's sweet.
Whenever the window is minimised to a smaller width than the theme, scrollbars appear at the bottom of the page and when you scroll to the right side, the header background does not completely cover the top of the page. I've been able to modify the default.css file so that the #blog-title and #blog-description background are the same as the #header and this improves the situation slightly although now I need the menu to go right across the page too.
Ideally I'd like the #header div to be 100% width but doing this changes nothing.
On a side note I've modified the theme slightly, so that it changes from 2 column to 3 column when it detects subpages and i've also coded in some random header images, but I don't think that this has caused the theme to behave like this.
Any help would be greatly appreciated.