If the <%DRAW%> function code displays in Firefox but does not display in IE, then this really might have more to do with an issue I've seen with IE than with Firefox. In my experience, if you are putting a certain draw function into a spot it is not designed to work in, the plain code will be rendered by the browser. However, when IE reads something that is possibly supposed to be VBSCRIPT type code like between <% - %> it hides these from displaying. Firefox does not hide these tags.
I believe the idea is that if the server does not correctly process the script tag (or the MC Draw function), and IE sees it, the browser does not visibly render it, but it still will be in the source code. Firefox does render the code visibly. It could be argued which browser is doing the right thing, as at different times hiding/displaying the non-functioning code might be exactly what the webmaster would want. IE makes it a little more difficult to troubleshoot, but it does hide your mistakes conveniently.
As an example, check out the following page in both IE and Firefox -
http://arconati.name/function-test.html - there is an ASP function that is supposed to display the current time, however, this is a static .HTML page so the code will not work. In IE, the code is hidden (but it shows in the source), in Firefox it is displayed.
Check and make sure that the script is working at all in either browser, not in the preview screen but on the actual site. From what you've described, my guess is that the specific script you are trying to use doesn't work in the spot you are trying to use it. I hope this helps!