ltsp-server error

[Luis Enrique Pomares Nuñez]

Hola recien he instalado un servidor ltsp y creado la imagen cliente
correctamente, los clientes  arrancan por dhcp y me sale la pantalla de
inicio de sesion en el cliente, pero cuando introdusco el usuario y la
clave  me sale un error diciendo: failed to load session 'ubuntu'
del lado del servidor  encontre estas lineas en los logs:
Jun 14 05:56:12 pvs-bxp dhcpd: DHCPDISCOVER from 00:1c:c0:57:7f:d3 via eth1
Jun 14 05:56:12 pvs-bxp dhcpd: DHCPOFFER on 192.168.1.253 to
00:1c:c0:57:7f:d3 via eth1
Jun 14 05:56:12 pvs-bxp dhcpd: DHCPDISCOVER from 00:1c:c0:57:7f:d3 via eth1
Jun 14 05:56:12 pvs-bxp dhcpd: DHCPOFFER on 192.168.1.253 to
00:1c:c0:57:7f:d3 via eth1
Jun 14 05:56:12 pvs-bxp dhcpd: DHCPREQUEST for 192.168.1.253 (192.168.1.1)
from 00:1c:c0:57:7f:d3 via eth1
Jun 14 05:56:12 pvs-bxp dhcpd: DHCPACK on 192.168.1.253 to
00:1c:c0:57:7f:d3 via eth1
Jun 14 05:56:12 pvs-bxp nbd_server[1191]: connect from 192.168.1.253,
assigned file is /opt/ltsp/images/i386.img
Jun 14 05:56:12 pvs-bxp nbd_server[1191]: Can't open authorization file
(null) (Bad address).
Jun 14 05:56:12 pvs-bxp nbd_server[1191]: Authorized client
Jun 14 05:56:12 pvs-bxp nbd_server[30344]: Starting to serve
Jun 14 05:56:12 pvs-bxp nbd_server[30344]: Size of exported file/device is
724312064
Jun 14 05:56:13 pvs-bxp nbd_server[1191]: negotiation failed
Jun 14 05:56:13 pvs-bxp nbd_server[1191]: Exiting.
Jun 14 05:56:20 pvs-bxp ldminfod[30346]: connect from 192.168.1.249
(192.168.1.249)
Jun 14 05:56:20 pvs-bxp ldminfod[30347]: connect from 192.168.1.253
(192.168.1.253)
Jun 14 05:56:27 pvs-bxp nbd_server[1191]: connect from 192.168.1.249,
assigned file is /opt/ltsp/images/i386.img
Jun 14 05:56:27 pvs-bxp nbd_server[1191]: Can't open authorization file
(null) (Bad address).
Jun 14 05:56:27 pvs-bxp nbd_server[1191]: Authorized client
Jun 14 05:56:27 pvs-bxp nbd_server[30364]: Starting to serve
Jun 14 05:56:27 pvs-bxp nbd_server[30364]: Size of exported file/device is
724312064
Jun 14 05:56:27 pvs-bxp nbd_server[1191]: connect from 192.168.1.253,
assigned file is /opt/ltsp/images/i386.img
Jun 14 05:56:27 pvs-bxp nbd_server[1191]: Can't open authorization file
(null) (Bad address).
Jun 14 05:56:27 pvs-bxp nbd_server[1191]: Authorized client
Jun 14 05:56:27 pvs-bxp nbd_server[30365]: Starting to serve
Jun 14 05:56:27 pvs-bxp nbd_server[30365]: Size of exported file/device is
724312064
Jun 14 05:56:27 pvs-bxp nbd_server[30365]: Disconnect request received.
Jun 14 05:56:27 pvs-bxp nbd_server[1191]: Child exited with 0
Jun 14 05:56:27 pvs-bxp nbd_server[30364]: Disconnect request received.
Jun 14 05:56:27 pvs-bxp nbd_server[1191]: Child exited with 0
Jun 14 05:56:53 pvs-bxp x-session-manager[30521]: WARNING: Session
'ubuntu' runnable check failed: Exited with code 1
Jun 14 05:56:53 pvs-bxp x-session-manager[30521]: WARNING: Unable to find
default provider 'metacity' of required provider 'windowmanager'
Jun 14 05:56:53 pvs-bxp x-session-manager[30521]: WARNING: Unable to find
default provider 'unity-2d-panel' of required provider 'panel'
Jun 14 05:56:53 pvs-bxp x-session-manager[30521]: WARNING: Unable to find
default provider 'unity-2d-shell' of required provider 'shell'