There are objects not displayed on google's map.

On the lower right corner of the website "http://www.vanaqua.org/cleanup/home.php", I typed in "Vancouver, BC, CA" in the "Find a cleanup site near you" box. A google map appeared at the center of the screen and there should be green, blue, and red balloons on the map. However, they didn't show up on my computer. Can anyone help me with this problem? Thanks a lot.
My system: Windows XP service pack 3 & I.E. 7.0