Graph does not show on server

Hello,

I've developped an ASP.NET website in VS 2005. It works with the built-in Crystal Reports.
All my reports are working both on my local comuter and on the server. When I create a report with a graph on it, it's displayed properly on the local computer.
When I look at the report with the graph when it's located on the server, I can't see it. The only thing displayed is a small icon marking that there's an image missing.
I know I miss something on the server but I don't know exactly which files. Could please somebody help me out?

Greetz