I hope this helps . Based on your trace output it looks like you are retrieving the wrong value from your dataProvider to set as the source. Without seeing your actual data, it's hard to know what the exact issue may be. That said, I would re-work your itemRenderer a bit. First, you don't need to put a single image in an HBox. Just use an Image. Also, you should not need to specify the height in the Renderer, the DataGrid should take care of such positioning.
<?xml version="1.0" encoding="utf-8"?>
public var imgPath:String;
override public function set data(value:Object):void
super.data = value;
how many item render instances will be created for flex data Grid