rhel5 problem creating virtual machine

[Susan Baur]

I've just installed rhel 5 on a test box wit the virtualization  
kernel. I'd like to start exploring the virtualization that's part of  
rhel 5 but when I try to create a guest operating system I receive  
the following error.

# xm create wg1 -c
Using config file "/etc/xen/wg1".
Error: destroyDevice() takes exactly 3 arguments (2 given)

here are the non-comment lines from my wg1 config file
kernel = "/boot/vmlinuz-2.6.18-8.1.1.el5xen"
memory = 64
name = "WebGUI_1"
vif = [ '' ]
disk = [ 'phy:hda1,hda1,w' ]
root = "/dev/hda1 ro"
extra = "4"

If I run it as a dryrun, i get the following
# xm create wg1  -n
Using config file "/etc/xen/wg1".
(vm
     (name WebGUI_1)
     (memory 64)
     (vcpus 1)
     (image
         (linux
             (kernel /boot/vmlinuz-2.6.18-8.1.1.el5xen)
             (root '/dev/hda1 ro')
             (args 4)
         )
     )
     (device (vbd (uname phy:hda1) (dev hda1) (mode w)))
     (device (vif))
)

Any ideas on where to start? This is my first foray into Xen, so any  
help would be appreciated

--Susan