I believe that Vista treats CFG files as protected system files. Try Ashar's suggestion here --> http://www.simviation.com/cgi-bin/yabb2/YaBB.pl?num=1193114568
Interesting, because I never had any probelms with editing my cfg files with Windows Vista..
I think the problem has been resolved now. It's a security issue with Vista. I don't use Vista myself but imagine that whether you have the problem or not would depend on your security settings.
1000Hourprivate asked why he couldn't save changes to a CFG file in FSX after editing it. Vista users have reported this problem before & it's nothing to do with FSX. In an attempt to explain it I was repeating something I read on this forum & I could be wrong.