This is a note for my future self, because something tells me I'll come across the same problem again....
The old server ran Colfusion MX 6.01, the new server is running Open Bluedragon, the near equivalent to Coldfusion 7 or 8. (Colfusion MX6.01 doesn't work properly with Apache 2, or more recent linux operating systems and I couldn't justify the upgrade cost to the latest version of coldfusion. My next big project will be to rewrite the Roots web site into an open source language though as Open Bluedragon runs coldfusion code and is open source, I might be able to develop rather than re-write from scratch, anyway, enough of that background).
Things change between program versions and to my horror I found the shopping cart wasn't working yesterday. The blame lies with me, I didn't properly test and I should have spotted it before the server move. Hey ho, 3 hours to debug and fix, and the problem was with
<cfset this = val(evaluate(listgetat( form.FIELDNAMES, listcontains( form.FIELDNAMES,"_ID_"))))>
The Fieldnames are coming out as all lowercase, and the original code was written to handle the form.FIELDNAMES returning all uppercase.
If i've a bottle of white wine at home, I'll open it and have a glass to celebrate my satisfaction :-)