I was following the tutorial at http://www.howtoforge.com/centos_5.0_xen I was not aware that virt-manager is GUI only.
Xend does start and I can do everything listed in the tutorial until I get to the virt-manager part.
What command line do you use to create a virtual server with virtsh? I am running as root, so that shouldn't be the issue.
The hardware does support virtualization and that is switched on in the BIOS.
I just looked at 'man virt-manager', I think it's safe to say it is a GUI-only tool.
AFAIK, virsh is a general purpose RedHat virtualisation tool which can manage Xen but will also manage KVM when that goes mainstream.
xm on the other hand is a Xen-specific tool.
Both can be used to do much the same thing, but are reasonably involved, so your best bet at this stage is 'man virsh' and 'man xm'.
Sorry but as I said, I'm a Xen newbie myself and have only used the GUI tool to date.