I was trying to install new Ubuntu 14.04 on XenServer 6.2, and all was fine untill reboot.
I'v bean able to install the system, but after that, when I was trying to start my fresh VM in Logs tab i saw something like this:

Here is a quick and working solution:

First thing you must do is to log in to the XenServer and edit the bootloader file of your new vm:

[root@iq-dev-xensrv01 ~]# export EDITOR=vim; xe-edit-bootloader -n vm1 -p1 

Where -n is name of the VM and -p is partition number

This command will edit grub config. Near line 145 you will find a submenu entry, like this below:

submenu 'Advanced options for Ubuntu' $menuentry_id_option...

Delethe whole segment, save changes and go to the next step.

Get the VM UUID

 [root@xensrv ~]# xe vm-list 
 uuid ( RO)           : cf669fe3-2542-bb18-2e39-96d8a8515a80
      name-label ( RW): vm1
     power-state ( RO): halted

and set the PV-bootloader and PV args like this:

 [root@xensrvx ~]# xe vm-param-set uuid=cf669fe3-2542-bb18-2e39-96d8a8515a80 PV-bootloader-args="--kernel=/boot/vmlinuz-3.13.0-23-generic --ramdisk=/boot/initrd.img-3.13.0-23-generic"

 [root@xensrv ~]# xe vm-param-set uuid=cf669fe3-2542-bb18-2e39-96d8a8515a80 PV-args="root=/dev/xvda1 ro quiet"

Change the kernel, ramdisk and root partition according to that you have in your vm. These are my settings. If you dont change this, its a big chance that you will get this kind of error

If everything is ok new machine should boot withount any errors.