popups on shapes...

If I bind a popup to a circleMarker, I seem to lose the popup after I zoom in on the map.  In a loop I create a number of circleMarkers and assign them to an array.  And place the array in a layerGroup.  

    shape = L.circleMarker(adjustedLatLng, { radius: 5, color: color, opacity: 1, fillOpacity: 1 });

    shape.bindPopup(modelPoint.HoverText);
    shape.on('mouseover', function (e) {
        this.openPopup();
    });
    shape.on('mouseout', function (e) {
        var shapeCoord = this.getLatLng();
        if (shapeCoord.distanceTo(e.latlng) > 50)
            this.closePopup();
    });