I have been working with few CSS menu before but this one is something I can't get my head around!
Have a look at www.handsthattalk.co.uk/index.php
Compare it between Firefox and IE 7. On IE 7, you will see the gap on top of page plus the gaps in menu!
I'm not sure if it's the bug in IE 7 because I had tried every way to close the gaps!
I have tried Holly Hack for menu and it worked but only there is a big gap on top of menu. I don't know if I'm doing something wrong!