THIS IS A SPECIAL REPOSITORY WITH A COMPILED KERNEL FROM XEN.ORG !!!
IF YOU UNSURE, PLEASE USE THIS REPO INSTEAD:

http://www.gitco.de/repo/xen3.4.0/

IF YOU LIKE TO TRY IT, PLEASE CHECK THIS: (BUT ONLY ON CentOS5 x86_64):

#> cd /etc/yum.repos.d/
#> wget http://www.gitco.de/linux/x86_64/centos/5/xen-3.4.0_with_kernel/gitco-xen340-kernel-testing.repo
#> yum install kernel-xen.x86_64 xen.x86_64 virt-manager.x86_64 virt-viewer.x86_64

THEN CHECK GRUB, IF THE HYPERVISOR AND KERNEL ARE CORRECT:

title CentOS (2.6.18.8_xgb340.1.el5xen)
        root (hd0,0)
        kernel /xen.gz-3.4.0_xgb340
        module /vmlinuz-2.6.18.8_xgb340.1.el5xen ro root=/dev/vg00r0/lvol0 elevator=cfq
        module /initrd-2.6.18.8_xgb340.1.el5xen.img

#> reboot

THIS ALL IS STILL UNSTABLE, BUT IT WILL CONTINUALLY IMPROVE FROM DAY TO DAY

THANKS,
SASCHA