I could be wrong, but on first glance at
http://code.google.com/apis/chart/image/docs/gallery/bar_charts.html#bar_types the example for bvo is missing pipes between data sets:
chd=t:
10,50,60,80,40
50,60,100,40,20
30,30,75,20,60
should be:
chd=t:
10,50,60,80,40 |
50,60,100,40,20 |
30,30,75,20,60