Problem with Graph Options in KPI Details Screen

Good Night

When I navigate into KPI Details screen almost everything works fine But there is a problem when I try to use the Graph Options in the KPI Details - There is no option appearing and Graph section is blank !

In IE7 a warning message appears hidden with the text : Chart Mode not defined

The strange is that Graph works in the Report section but does NOT work in KPI Details Why should not this option appears ?

Regards,

Alfred