It was sorted out by completely avoiding the problem in the end.
Originally I needed the 'OnLoad' command for the way the page was run.
In the end I could run the page directly from the servlet (i.e no need to call it from 'OnLoad')
Therefor avoiding the Netscape 'OnLoad' problem.
I've got an ongoing topic at http://www.devshed.com/Talk/Forums/Forum1/HTML/000544.html to see if anyone knows what the problem could have been....
cheers
Ben