graph images missing..

[clubbing80s]

Hi.
when I click on a graph in a screen, it goes to the page where the, graph should be displayed
but the image is missing ..
Graphs are only displayed in the configuration interface and in the screens page, any where else the images are missing ..
Running on FC 5 mysql 5, php 5, browser is firefox 1.5

Many Thanks

[SLMitch]

There is a bug of php session :
choose group ALL when you choose or click on a graph, items, trigger, ...

[clubbing80s]

I guesed as much, but in wich files do I start looking in to debug it ?