I ran into this issue too.
What can I say? It's IE!
anyways...I did however find a way to get it to work in IE.
instead of assigning the value to window.status directly, we let settimeout do the dirty work (it's not that the onMouseover event doesn't work.....just setting the window.status in an onMouseover in an AREA tag).
And in the onMouseover, replace "window.status" with the function name or u can enter the setTimeout call there.
setTimeout("window.status = \'" + text + "\';", 0);
onMouseOver="window.status='hello World!'; return true;"
And it works fine in Firefox and in IE.
onMouseOver="return setStatus('hello World!');"