Telerik control do nothing on click in 2nd window

In my main browser window I launch a page (aspx) in a new window via window.open, on this new window I have RadDatePickers. But when I click on these control nothing happens. ie/ the calendar popup does not show up for me to pick a date

The RadDatePicker works fine on the main browser window thoughts?

Due to javascript error caused by telerik update (telerik RadTabStrip's ReorderTabsOnSelect)

Solution: https://www.telerik.com/forums/radtabstrip-producing-js-errors

Before any RadTabStrip, add the following:

        <script type="text/javascript">
        if (Telerik.Web.UI.RadTabStrip) {
            Telerik.Web.UI.RadTabStrip._getTabGroups = function (listElement, sizeProperty) {
                var groups = [];
                var currentGroup = [];
                currentGroup.size = 0;
                Array.add(groups, currentGroup);

                var listItems = $telerik.getChildrenByTagName(listElement, "li");
                for (var i = 0; i < listItems.length; i++) {
                    if (listItems[i].className == "rtsBreak") {
                        currentGroup = [];
                        currentGroup.size = 0;
                        Array.add(groups, currentGroup);
                        continue;
                    }

                    var sizeToAdd;

                    //In all browsers exept IE8 and above the actual size contains fractions of a pixel which are rounded when offsetWidth/offsetHeight properties are used.
                    //Use getComputedStyle instead to sum the actual size and then round it up, otherwise the last tab will fall on the next row.
                    if (!($telerik.isIE7 || $telerik.isIE8)) {
                        var computedStyles = getComputedStyle(listItems[i]),
                            computedStyle = 0;

                        // invisible items break logic as .width returns "auto"
                        if (computedStyles && $(listItems[i]).is(":visible")) {
                            computedStyle = sizeProperty == "offsetWidth" ? (parseFloat(computedStyles.width) + parseFloat(computedStyles.paddingLeft)) : parseFloat(computedStyles.height);
                        }

                        sizeToAdd = computedStyle;
                    } else {
                        sizeToAdd = listItems[i][sizeProperty];
                    }

                    currentGroup.size += sizeToAdd;

                    Array.add(currentGroup, listItems[i]);
                }

                if (!($telerik.isIE7 || $telerik.isIE8)) {
                    Array.forEach(groups, function (group) {
                        group.size = Math.ceil(group.size);
                    });
                }

                return groups;
            };
        }
    </script>