FYI - I found another situation that can cause this to occur. I was adding a grid to an items collection of a panel and at the same time I had the html property set to a value. By getting rid of the html property, the error went away.
//html:'Middle-North Content', // Commenting this line out fixed the problem
items:[aGrid] // having the items set with the html property above caused the createRange error (in IE only)