Maybe try using window.top.document instead of parent.screen, window.top is also compatible with all browsers, where the parent object isn't. Netscape doesn't see iframes as child objects (im assuming this is an extension to the refreshing script I helped you with earlier that used iframes), so the code above will never work in netscape. I think IE has problems with the parent/child relationships sometimes too, as I remember doing something similar where I had to use window.top instead of parent to get it to work in any browser.
Also, when executing the script from the same frame as what you need the innerHTML of, you can access it with document.body.innerHTML instead of putting the window/frame id/name in front of it.