Maybe I do have shockwave disabled -- couldn't find anything about it. I don't have any extensions or plugins with FF so maybe that's all I would need.
I do see that header in IE -- and I guess that's what causes the soundfile, too? Personally, I hate sites that automatically load soundfiles -- can you add controls that allow a user to turn off the sound?
The difference I see between FF and IE is that in FF the ends of the paint splashes start at the top of the middle section with the three columns. In IE, paint stripes start there, and end with those splashes at the bottom.
I honestly don't know enough about the browser differences to understand why this is happening. Still, I wonder if it has anything to do with whether that striped background is assigned to the page class or the wrapper class, or if it matters that your footer div is inside the page div.
EDIT -- very odd, but after opening the page in IE, suddenly the header also appears in FF. And I see you do have a sound off control -- for some reason the complete header didn't load in IE and didn't show that control. My apologies.