Do it simply by adding a class to the body:
.stop-scrolling { height: 100%; overflow: hidden; }
Add the class then remove when you want to re-enable scrolling, tested in IE, FF, Safari and Chrome.
$('body').addClass('stop-scrolling')
For mobile devices, you’ll need to handle the touchmove event:
$('body').bind('touchmove', function(e){e.preventDefault()})
And unbind to re-enable scrolling. Tested in iOS6 and Android 2.3.3
$('body').unbind('touchmo