I tried this:
<body onload="setSize(); $('#slider').nivoSlider();">
And also tried temporarily removing all the nivo slider code and nothing seems to do it.
An interesting note is that if I resize the ie window and then maximize it again everything kinda snaps into place and looks just fine.
Also I tried this to check it didn't have anything to do with timing:
var firstLi = $('#hotelSlider').show().find('li:first-child');
var firstHeight = firstLi.height();
var container= $('#hotelSlider');
'height': firstHeight + 'px'
Chrome and Firefox wait for the 5 seconds and resize, IE insists in making my life a living hell...