I'm sorry, but the code is identical.
The HTML code associated with the DIV containing the rotuine is an include file for both pages.
The javascrip file is the same .js file used by both pages
The php code is the same identical routine for both pages.
The DOM for both pages are well-formed and correct.
The pages do differ outside of the DIV's dealing with the AJAX, but both pages pass HTML checks for proper coding, and I have checked the DOM of each about 5 times to insure they are well-formed.
The OLNY difference is code is that for IE7:
xmlhttp = new ActiveXOblect("Msxml2.XMLHTTP");
and for firefox: xmlhttp = new XMLHttpRequest();
Both pages work consistently for Firefox. I can and have traced each variable and each outcome of each line of code using Firefox tools. IE7 works fine under the first page I pull up. but fails on the second page. The error is a wonderfully descriptive statement, "Unknown runtime error".
There are global state variables in the .js code which, if IE7 used the same instance of .js for both pages, might screw things up, but in theory I am bringing in a new instance with a new page call. Such is the case in Firefox. Also, there may some peculiarity with activeX that I don't understand, since I am weak in XML, but what?
I have to think that if the essential code works well for Firefox, I am dealing with some subtle issue in IE7, classed as an "unknown runtime error".
Thank you for your comments.