Hello.
Yesterday I tried installing Fedora 10 and Fedora 11 i386 Xen domUs/guests using virt-install and/or virt-manager on CentOS 5.3 Xen x86_64 dom0/host.
It doesn't work. The guest kernel crashes early and the graphical VNC console newer shows up.
Installing x86_64 domU on x86_64 dom0 work well. 32-on-32 works aswell. So it's a 32-on-64 bug.
CentOS 5.3 32b guest on x86_64 host works though, most probably because it uses the "original" Xenlinux patchset.
I found the upstream bug: https://bugzilla.redhat.com/show_bug.cgi?id=467698
This problem will be fixed in upcoming RHEL 5.4, and it's also fixed in the latest el5 test kernel-xen (-159).
I think this is not really F10 or F11 guest specific, but more likely will happen with any/many upstream (kernel.org) pv_ops Xen domU kernels.
-- Pasi