If you try to add style declarations in the head of a document, IE borks at the name 'style' - "unexpected call to method or property access".
I guess its getting confused between the head element and the object property .style?
var t = document.createElement("style")
t.setAttribute("type", "text/css");
t.setAttribute("media", "screen");
var temp_text = document.createTextNode(v + " {visibility:hidden}");
t.appendChild(temp_text)
Where v is id of a flash object.