This is really bizarre. Although it works on your website fine in IE. I can't get it to work on MINE. If you have any insights, they'd be much appreciated.
From this website http://webdeveloperplus.com/jquery/quick-easy-way-to-implement-drag-n-share-with-jquery/
"To get this script to work correctly in IE, you will need to set margin and padding values in the style-sheet for anchor elements which are draggable."
The issue is with the ps_tooltip variable. Global variables and DOM element ids share the same namespace. Since ps_tooltip is declared as both a variable AND as an ID for a DOM element, the two conflict with each other, which is what's causing issues in IE.
In jquery.prettySociable.js, replace: ps_tooltip = $('<div id="ps_tooltip"> with var ps_tooltip = $('<div id="ps_tooltip"> The 'var' keyword scopes the ps_tooltip variable to tooltip.show(), resolving the conflict.