Google Maps Aimation - App halting at polyline.Distance();

I wonder if someone can help with my stalled Google Maps application. I am adapting the animation features of this example are on the geocodezip, for example Multiple Marker Aimation. The general code for the startAimation sequence looks like this.

`function startAnimation(index) {
   if (timerHandle[index]) clearTimeout(timerHandle[index]);
   eol[index] = polyline[index].Distance();
   map.setCenter(polyline[index].getPath().getAt(0));

   poly2[index] = new google.maps.Polyline({
   path : [ polyline[index].getPath().getAt(0) ],
   strokeColor : "#FFFF00",
   strokeWeight : 3
   });
   timerHandle[index] = setTimeout("animate(" + index + ",50)", 2000); 
   // Allow    time for the initial map display
   currentDistance[index] = 50;
}`

I have the example applications working properly but when imbedded within my application the startAnimation fails at the statement

 `eol[index] = polyline[index].Distance();`

Does anyone have any insight into why this is happening. I am presently climbing the steep learning curve that is Google Maps but looks like I am stuck on a ledge - can someone give me a lift up please?

Just for info, the index terms refer to the multiple markers and do not affect the behaviour.