I am a new customer also experiencing this issue, so I figure I might as well add to this thread.
My environment is ASP.NET 2.0 VB also using the AJAX Toolkit.
Utilizing the RenderChartHTML method yields the "non-secure items" warning in IE, all is well in FF as usual.
When switching to the standard RenderChart method the "non-secure items" warning goes away but then any charts to be rendered on my AsycPostbacks fail.
To try to compliment both issues I attempted to use RenderChart on Page_Load and during Postback use RenderChartHTML but that still brings the "non-secure items" warning.
I am quite new to the FusionCharts component and am not sure where to go from here....
Any pointers?