If you go to http://showcase.richfaces.org/richfaces/component-sample.jsf?demo=extendedDataTable&sample=exTableSelection&skin=blueSky in IE9 and click down on 1 row and release on another a JS error occurs in :

richfaces.ui.ExtendedDataTable.selectRows: function(range) {
if (typeof range == "number") { range = [range, range]; }
var changed;
var i = 0;
for (; i < range[0]; i++) {
if (this.ranges.contains) { this.deselectRow(i); changed = true; }
}

At the for loop while trying to access range[0].

The IE JS Console Log is

SCRIPT5007: Unable to get value of the property '0': object is null or undefined
packed.js, line 10109 character 24