Higher Z-order layer appears behind dropdownboxes

I did some more research on Google and other forums and found that there is a bug in MSIE where for some controls it uses Windows controls instead of web controls and these windows controls display above everything on the page no matter the z-index. Dropdownlists are one of these.

One of the solutions I have found is to put an iframe behind your tooltip. I am still having a problem with some of my SPAN tags showing through AFTER a tooltip has been displayed for them (i.e. another they show through another tooltip from a different element)