The is_ie is one of the flags I've seen in javascript to check for which browser is being run.
Although I use a lot of MS products (I have an MSDN subscription), I'm not their biggest fan.
It sounds like the javascript interpeter that your version of IE is using is broken. You can upgrade it, but if the problem persists, you might look at mozilla or opera, or one of the other browsers out there.
Sorry I don't have a "just do x and your problem will go away type answer"
:devil: