I have recently upgraded from Redhat 6.0 to 6.1 on two machines, and have noticed that the logout dialog box in Gnome now seems to be unavoidable. I've tried unclicking the "Prompt on logout" button in the "Startup Programs" window of the Gnome Control Center, but it doesn't seem to work.
I have verified this to be a problem on a 6.1 machine in the lab. I am assigning this to a developer for further review.
This appears to have been fixed subsequent to the release of 6.1. (There was an extra character in the code that retrieved the config option.) We should be releasing updated RPM's of "October GNOME" soon that will include this fix. Installing the October GNOME RPM's from ftp.gnome.org would also fix this problem, though they may not integrate perfectly with Red Hat 6.1 in all areas.