I still haven't been able to fix mine either ... BUT ... as a temporary fix, if I switch from  HTML to Plain Text or Rich Text (under the Format Text tab) in Outlook, then switch back to HTML, it will remember any changes I made from the default template.

Is it a huge pain in the A to do this on every email?  Yes.  Do I remember to do it all the time? No.  But, it works when I really need it to. 

I would still LOVE to find a permanent fix.