editing yum.conf

[Peter Lesterhuis]

When trying tot modify yum.conf from the command line (terminal - su - 
password root - gedit /etc/yum.conf) and saving this modified file I get 
the following error:

(gedit:3062): GnomeUI-WARNING **: While connecting to session manager:
Authentication Rejected, reason : None of the authentication protocols 
specified are supported and host-based authentication failed.
[root at localhost peter]#

No modifications appear in the yum.conf file.
How to solve this?
Peter.