On a machine with X installed but not gnome-core, rhn_register fails with a traceback error. Installing gnome-core, or unsetting DISPLAY, makes it work. It would be neat if it could figure out that the GUI isn't going to work and pretend that DISPLAY is unset if it comes across this situation.
I have written a python wrapper for rhn_register which is currently in testing. Should certainly solve this little issue (jkt; 1/18/01)
Reassigning to Adrian. This functionality should be present in the next release of rhn_register, as it is working in CVS currently.