(random) "no image display" under Netscape

[User (Legacy)]

Some users with Netscape (4.61 or prior) report random "non image display" 

when 

accessing a chart (PNG format). 

However, the missing image is generated on the server (IIS 4). 

We can not reload the chart, as this action generate another image, which 

may also 

not be displayed. 

No such problem has been encountered with Internet Explorer 

Is this a known problem with Netscape ? Is there a turnaround ? 

Thanks, 

   Christophe.