Something

[root@soulcube /]# cat /etc/xen/centos.5-0.xen3.cfg
#kernel = "/boot/vmlinuz-2.6.18-8.el5xen"
#ramdisk = "/boot/initrd-2.6.18-8.el5xenU.img"
bootloader="/usr/bin/pygrub"
memory = 256
name = "scalix"
vif = [ '' ]
dhcp = "dhcp"
disk = ['phy:vg0/scalix-root,hda1,w', 'phy:vg0/scalix-swap,hda2,w']
root = "/dev/hda1 rw"

[root@soulcube /]# xm create -f /etc/xen/centos.5-0.xen3.cfg
Using config file "/etc/xen/centos.5-0.xen3.cfg".
Traceback (most recent call last):
  File "/usr/bin/pygrub", line 497, in ?
    g = Grub(file, isconfig)
  File "/usr/bin/pygrub", line 152, in __init__
    self.read_config(file, isconfig)
  File "/usr/bin/pygrub", line 342, in read_config
    raise RuntimeError, "we couldn't find grub config file in the image provided."
RuntimeError: we couldn't find grub config file in the image provided.
No handlers could be found for logger "xend"
Error: Boot loader didn't return any data!