Pie chart issue with WAD

Hi Experts,

When I try to execute a query through Web Application Designer with a form of Pie chart, its not working properly. All I'm getting in web dash board is just a circle with blue color. Its similar to the first picture in the below image.

http://img296.imageshack.us/img296/1450/question3hn0.jpg

But I'm getting correct output with Column chart.

Could someone please help me to resolve this problem?

Bregards,

Bala