X server, that is (as opposed to my ex-spouse...) Anyway, I was loving life with my rebuilt 2.4.21-9.0.1.EL.c0custom041130a kernel, and then ran "yum update", which gave me a grub line for 2.4.21-20.0.1EL, but the 21-20 not only won't work with the old X settings, I can't get it to set up X at all. I tried running "yum update" from a console on this kernel, but yum can't find the conf file unless I tell it where it is with the -c switch, and even then it won't follow the symlink from /etc/yum.conf to /etc/centos-yum.conf. Once I supply the proper switch and path then it starts the update and chokes on the GPG keys for php-mysql. As directed in the error message I've tried running yum clean and also tried removing the /var/.../php-mysql... file indicated, to no avail.
That said, all helpers appreciated.