If you close the Explorer window showing your images and then open it again, do the thumbnails get refreshed/updated?
By the way, you're using a 46,395 byte, 433x434 pixel image to display a 65x65 pixel avatar. How about taking this resized (3,321 bytes and actually 65x65 pixels) version of your image and using it for your avatar?
Please put it on your own image hosting server. To save it to your hard drive, just right click on it and Save Picture As ....