iSCSI boot and XEN hypervisor

[CGen]

Hello!

I recently installed a new Ubuntu 13.04 server directly on the iSCSI-drive. In the installer there is a great opportunity to do so.

Then I set everything to download using iPXE. Everything is working fine.

I then installed the xen hypervisor on the server.
Grub menu is displayed. I choose the item with Xen. grub displays a message that the kernel is loaded. Then a black screen and all.
I can not understand why.

Can anybody help?

Kernel and initrd.img is same in the case with Xen and without it.