I have a problem computer in my care.
I have a user, he uses outlook web access when at home or on trips. In OWA, he has a signature. It works fine for me on my home machine (IE 8, Win7) if I log in as him and post it, it works fine on one of his old machines (IE 8) if I log into OWA and post it, but if you log in on his Windows 7 / IE 8 Sony Vaio and post a signature, it will look fine in the message you're editing but the end user will see "Error! File not specified".
Looking at a one-word message from each of these machines with signature attached, the working ones are a few lines of HTML (img src, href, etc..). The one from IE / OWA on the non-working machine is a page of XML comments that mention many Office products (excel, office 2007, something else) and other things such as sharepoint, openxmlformats, passport.com,officenet conferencing, etc.
I've restarted IE with no addons, no change.
Server it's connecting to is an exchange 2003 system.